“We made them imams, guiding by Our command, and We revealed to them the performance of good deeds, the maintenance of prayers, and the giving of zakat, and they used to worship Us” (21:73).
This is a case where good leadership takes place; they guide others religiously by Allah’s command. On the other hand, the Qur’an describes those who invite others towards hell:

“We made them leaders who invite to the Fire, and on the Day of Resurrection they will not receive any help” (28:41).
At any rate, whether an imam is a good or corrupt person, an imam is nonetheless an important person; everyone on the Day of Judgment will be resurrected with and identified by the name of his or her imam (instead of calling us by our individual names) regardless of his moral standing:

“Remember the day that we call every group of people with their Imam” (17:71).
Even Pharaoh, as said in the Qur’an, will be the leader of his people on the Day of Judgment, though he will lead them towards hell (11:98). Thus, leadership in this world is reflected in the next world. A good Imam will take his people towards heaven, while a corrupt one will lead them to punishment.
Technical meaning: When we say Imamate is one of our principles of faith – that whoever dies not knowing his imam will die the death of the Age of Ignorance – we do not mean an Imam is merely someone who leads the society regardless of his moral status. Here, we have a technical sense. Before describing the technical meaning of the term Imam, it is necessary to present the roles of the Prophet Muhammad (s) in order to have a background for the concept of Imamate.

The functions of the Prophet (s)

1. A Messenger
All Muslims agree that one of the Prophet’s tasks was deliverance of the message. He was to deliver the revelation, which was about practical laws, beliefs, and morals. There is no doubt among Muslims that this is the role of the Prophet protected by Allah so that the message can truly and purely reach the people. The content delivered from Allah to the people was without the slightest alteration.
He presented the divine message with utmost accuracy and care. He did not and could not add something as small as a letter to the Qur’an. It has to be noted that although all Muslims unanimously agree that he was infallible, i.e. protected from mistakes and sin, there different views with regards to when one can be infallible. The Shi‘a believe that all Prophets were infallible before and after their Prophethood.
They had comprehensive infallibility (‘ismah). On the other hand, some non-Shi‘a theologians believe in the Prophet’s infallibility in relation to delivering Allah’s message, but at the same time they believe that the Prophets may have committed sins and mistakes in their personal life or before they had become Prophets.

2. A Judge
According to Islam, a legitimate judge receives his authority from God; otherwise no one can impose his verdicts on people since they are all created by God to be free. No one can impose something on a free person without being given authority by Allah (swt). As free people, I have no authority upon you, or you upon me. But a judge has authority.
The source of authority is from Allah. Of course, it is possible that opposing parties may agree on having an arbitration (qazi takim). Here the authority of the judge comes from the both parties and he has no authority to settle the issue without them wanting in the first place to do so. For example, after Prophet David fulfilled his responsibilities and passed several trails, Allah told him:

‘O David! Indeed We have made you a vicegerent on the earth. So judge between people with justice, and do not follow desire, or it will lead you astray from the way of God. Indeed those who stray from the way of God —there is a severe punishment for them because of their forgetting the Day of Reckoning.’ (38:26)
In the chapter al-Nisa 65, we read:

“But no, by your Lord! They will not believe until they make you a judge in their disputes, then do not find within their hearts any dissent to your verdict and submit in full submission.”(4:65)
Thus, a believer must accept anything the Prophet decrees.

3. A leader of society, a head of state
The Prophet ruled the Islamic society. He did not encourage assembling in a mosque for prayers and recitations and let someone like Abu Sufyan rule.7
The Prophet exercised political leadership after he arrived in Medina.

Shi‘a and Sunni views on the qualifications of an Imam
The three above tasks of the Prophet, in that he acted as 1) a messenger, 2) a judge, and 3) a political leader, should be examined in order to decide who is qualified enough to be his successor. It is important to note that not all Prophets were political leaders. The first task, being a messenger, was shared by all of them. Some held the second and third position as well.
This raises the question as to whether or not an Imam should inherit the last Prophet in all three tasks or only in political leadership. Normally Sunni theologians believe that only the third and perhaps the second tasks must be continued after the Prophet by his successors or the caliphs. This justifies the necessity of an Imam. They also hold that it is left to the people to choose who the successor of the Prophet will be.
The candidate does not need to be the most knowledgeable person or even very knowledgeable about Islam because he does not have the task of teaching Islam. Neither does he need to be infallible nor the most pious member of the society. According to many of them, even if a prince kills his father and takes over his position he must still be obeyed in the same way that his father used to be obeyed.
The Shi’a believe in the necessity of a political leader after the Prophet as well as its continuance, although this task does not suffice. The Prophet received the full package of Islam. Allah revealed to him all that was necessary, the final message, with no further revelation. But the Prophet could not deliver Islam in its completion with all details to the people in a period of 23 years.
Not only the time was not enough, but also the people were not prepared to be given all details. There were many aspects that they could not understand, because they had no clue about them and specific state of affairs did not yet arise at that time to make them even think about them, let alone inquire about them.
Thus, the Prophet taught Imam Ali everything about Islam and then the Imamate was transmitted to his sons Imam Hasan and Imam Husain, and their descendants, until it reached the 12th Imam, Imam Mahdi (aj). This knowledge was not the conceptual or theoretical knowledge a student acquires at school. This was a knowledge given by Allah (swt) with a special provision.
The Prophet said, “I am the city of knowledge and Ali is its gate. Whoever wants to access this knowledge must enter this city through its gate.” Imam Ali said, “The Prophet opened for me a gate of knowledge, from which 1000 further gates were opened and then from each of them another thousand gates were opened for me.” This is not quantitative knowledge. It covered everything needed and was given at once.
Islam is to be properly taught by an Imam without having to receive any further revelation. Therefore, in addition to acting as a political leader, the Imam must be the most knowledgeable person in the society. This knowledge is given immediately and directly by Allah (swt) through the Prophet without having been schooled. It is knowledge and wisdom that have been placed in the heart and mind of the person.
Political leadership is not the main task. Indeed, most of Imams could not exercise their political leadership as they were imprisoned or under house arrest. Nonetheless, they were still Imams. What makes them an Imam is their duty of flawlessly delivering the true message of the Prophet.
The Prophet’s time was an era filled with conflicts, when Muslims bore oppression trying to defend themselves and Islam; the message was not taught in the comfort of an academic institute. Moreover, the people were not prepared enough. Many embraced Islam in the later years of Islam.
Few embraced Islam in Mecca and out of those few some migrated to Ethiopia to escape the oppression. The educational level was still low as it was not very long after the Age of Ignorance. Illiteracy was rampant as the literate ranged from a total of ten to twenty people. Events that required an Islamic response did not yet emerge because normally problems cannot be anticipated and the solutions offered before the problem actually occurs.
It was a gradual process in which Muslims faced new challenges and civilizations. When it comes to practical rulings, the Qur’anic message is very general. For example, the Qur’an indicates that prayer is mandatory, but most of the details about prayer are not mentioned in the Qur’an. If practical matters were discussed in the Holy Book, it would be a rather large book, difficult for people to review and reflect on.
Thus, the Prophet delivered the message properly though he did not have the chance to fully deliver its details. So what must be done with respect to new issues that emerge gradually?
Sunnis and Shi’as differ with regards to this. Sunnis believe that people must use their own views in the form of juristic preference (istihsan), deductive analogy (qiyas) and the like. Shi‘as believe that such methods are not able to discover the religious rulings and, therefore, are not valid.
One has to refer either to the Qur’an and Sunnah or to decisive judgement of reason. Therefore, the Shi‘a first tried to preserve the Sunnah of the Prophet (s) by narrating and registering his hadith despite the ban made by the first three Caliphs on narrating and writing down the hadiths which continued up to the reign (99 to 101 A.H) of ‘Umar ibn ‘Abd al-‘Aziz, the Umayyad. Secondly, following the instructions given by the Prophet Muhammad (s), they referred to the Imams of his Household for guidance with respect to new or controversial issues.
Thus, instead of being in contact with an infallible for a mere 23 years, the Shi‘a enjoyed the access to the Infallibles for more than 300 years. When Imam Mahdi (aj) began his major occultation in 329 A.H., a total of 342 years was spent having access to the infallibles. Imams also trained some of their companions to act as jurists who could derive rulings from the principles given by the Prophet (a) and Imams (a).
Thus, people were gradually trained to know what to do in the time of major occultation of the 12th Imam.
Having comprehensive knowledge is another aspect of Imamate that is not necessary according to Sunni understanding of Imamate. No one doubts that the first three caliphs were not the most knowledgeable people of their time. For example, ‘Umar ibn Khattab, the second Caliph, on seventy occasions said: “If Ali were not there, ‘Umar would have been destroyed.”8
It has also been reported that when Abu Bakr died, and people cried in his house, ‘Umar asked them not to cry. As they continued to do so, ‘Umar cautioned them against it, saying, “I will punish you because I have heard the Prophet say that the dead person will be punished on account of those who cry for him or her.”
‘Aishah, angered at Umar’s misquotation, corrected and rephrased the hadith: the Prophet actually said that while the family of a deceased Jew was crying, the dead person was being punished, not because they were crying, but because of his own conduct. In reply to Aishah’s clarification, ‘Umar said, “If the women were not there, I would have been destroyed.” Thus, they do not claim that the Caliphs were the most knowledgeable.
According to the Shi‘a, delivering the message and having comprehensive knowledge are two traits that are prioritized in Imamate. Political leadership comes after the abovementioned two. Whether the Imam acts as a leader in society or not, he is the Imam. If the Imam is kept in prison all his life, or if he is in occultation, he is still the Imam.
And because he is qualified to deliver the true message of Islam, has piety and wilayah (which will be explained later) and it is only after having all of these requirements, that he is qualified to be a political leader. It is not because he is a political leader, he is the Imam; rather, because he is the Imam, he is a political leader. Why is he the Imam? Because he has the greatest knowledge and piety as well as wilayah.
Before delving into the concept of wilayah, we should study the status of the Household of the Prophet (Ahl al-Bayt) in Islam.9
For this purpose, we will try first to define who they are and secondly to demonstrate their authority. It should be noted that Ahl al-Bayt are slightly different from the twelve Imams, as it includes Lady Fatima (a), the daughter of the Prophet. Thus, though this discussion is about Imamate, the term Ahl al-Bayt is used because it includes Lady Fatima (a).

The status of Ahl al-Bayt
Who are the Ahl al-Bayt? The Shi‘a believe that the “Ahl al- Bayt” refers to the close relatives of the Prophet, namely Lady Fatima, Ali, and their children, Hasan and Husayn. Of course, according to the Qur’an and hadiths, their authority is extended to the succeeding Imams as well. Sunnis generally believe that all Muslim relatives of the Prophet are the Ahl al-Bayt. The children, wives, cousins, uncles, and aunts are included. The only exception they all have to accept is when a relative is a disbeliever (kafir) as some of the Prophet’s uncles were so.
There are different arguments for the Shi‘a position. Before we refer to those arguments, we should bear in mind that the Shi‘a position is the most cautious position and even if someone is in doubt about which position to hold, he can still follow the Shi’a position, because even non-Shi‘as accept that Lady Fatima, Imam Ali, Imam Hasan, and Imam Husayn are included. So the burden of argument is on those who extend the scope of Ahl al-Bayt beyond that.
First - a rational argument – is that sometimes we can better understand the subject of a ruling (hukm) by looking at the predicate. Studying the predicate clarifies the subject. If the Ahl al-Bayt are those to who we should appeal next to the Qur’an and if they will never separate from the Qur’an, it is easy to understand that those who fall under the title of Ahl al-Bayt must be special people.
They have such a high status that can be found only in very select group of the relatives of the Prophet (s). Everyone certainly excludes the unbelievers like Abu Lahab.
Then among those who were believers, who were those for whom the greatest knowledge of the Qur’an, perfect purity and immunity from going astray and conflicting the teachings of the Qur’an have been confirmed or even claimed? Is there anyone among the family of the Prophet for whom such a high position of infallibility is claimed other than Ali, Fatima, Hasan, and Husayn?
Does anyone have any other candidates to put forward? No one can say that there were people other than these four who were infallible and will have always accompanied the Qur’an. Literally the expression of the Ahl al-Bayt may be very broad in its scope, but we are looking for people among the relatives of the Prophet (s) who can satisfy the criteria - that is, constantly accompanying the Qur’an and never act against it.
Overall, they must always be a source of guidance for people. Who are they? Sunnis claim that no such person existed; other than the Prophet, they do not believe in anyone who was infallible. Even with respect to the Prophet (s), they generally limit his infallibility to delivering the message and not his personal life.
Second – there are hadiths from the Prophet Muhammad (s) which clarify the meaning of Ahl al-Bayt. In what follows, I will mention some hadiths narrated in major Sunni sources:
1) Muslim narrates from ‘Ayishah, Umm al-Mu’minin: The Prophet went out wearing a black woolen cloak, when Hasan the son of Ali came to him, so the Prophet let Hasan come in with him under the cloak. Then Husayn came and he too entered. Then Fatimah came. She entered as well. Then Ali came. He also went under the cloak, such that the cloak covered the Prophet, Ali, Fatimah, Hasan and Husayn. Then the Prophet recited:

‘God only desires to keep away impurity from you, O People of the House! And to purify you a (thorough) purification’ (33:33).10
2) Muslim also narrates from Sa‘d b. Abi Waqqas that he was asked by Mu‘awiyah why he refused to verbally abuse Ali. Sa‘d replied: I remember three sayings of the Prophet about Ali which caused me not to say anything bad about him. If I possessed even one of these qualities it would be better for me than red camels.11
The first was that when the Prophet wanted to go to the war of Tabuk, he left Ali in Medina. Ali was very sad at not having the good fortune to join the army and fight for the sake of God. He went to the Prophet, saying, ‘Do you leave me with children and women?’ The Prophet replied, ‘Are you not happy to be to me as Aaron was to Moses, except that there will be no prophet after me?’
Second I heard from the Prophet on the day of conquest of Khaybar: ‘Certainly I will give the flag [of Islam] to a man that loves God and His Messenger and is loved by God and His Messenger.’
We hoped to be given the flag, but the Prophet said: ‘Call Ali for me!’ Ali came while suffering from pain in his eyes. The Prophet gave him the flag and at his hands God granted us victory. Third when the verse of Mubahalah was revealed the Prophet called Ali, Fatimah, Hasan and Husayn and said: ‘My Lord! These are my household.’12
3) Ahmad ibn Hanbal narrates from Anas ibn Malik that when the Verse of Purity (tathir) (33:33) was revealed, for six months the Prophet used to call at the house of Ali and Fatimah every morning on his way to the mosque for the Dawn Prayer and say: Prayer, O People of the House! ‘God only desires to keep away impurity from you, O People of the House! And to purify you a (thorough) purification’ (33:33).13
Thus, for six months after this verse was revealed, the Prophet applied ‘Ahl al-Bayt’ every day to Imam Ali and Lady Fatimah to establish among Muslims that these are the Ahl al-Bayt. This hadith leaves no space to doubt that at least that these people are the most obvious instances of the Ahl al-Bayt and they must certainly be followed.
4) Zayd ibn Arqam was one of the companions of the Prophet. Many years after the death of the prophet people referred to him, pleading for narrations. He would reply, ‘I have become very old and have forgotten some of the Prophet’s sayings. So whatever I tell you accept it and whatever I do not tell you do not force me to tell you.’ What he clearly remembered was this: Once the Prophet stood up to speak to us in a place between Mecca and Medina called Khumm. The Prophet praised Allah and began his sermon: ‘Oh people, know that I am a human being and soon a messenger from Allah (the Angel of Death) will call me and I will answer.
Surely I am leaving among you two precious things: the first is the book of God, a guidance and light, so hold on to it. And the second is my household.’ He added three times, ‘I ask you to remember Allah regarding the way in which you treat them.’
Then Husayn ibn Subrah said: One of the people who were there asked Zayd, ‘Oh Zayd who are the household of the Prophet? Are his wives included?’ Zayd replied, ‘The wives of the Prophet are his relatives, but his household are those who cannot accept charity, unlike the wives who could accept it.’
He was then asked, ‘If the wives of the Prophet are not of the Ahl al-Bayt, who are they?’ Zaid replied, ‘The family of Ali. Aqil, Jafar, and Abbas.’ Zayd was not a Shi‘a and not a follower of the Ahl al-Bayt, but he knew to this extent that the wives are excluded, though he thought that all cousins of the Prophet are included.
It has to be noted that although the cousins of the Prophet (s) are considered as sayyid (descendants of Hashim) and therefore certain rulings apply to them, there are certain rulings that apply only to the children of the Prophet Muhammad (s) through his daughter, Lady Fatimah. Zayd knew that the wives are excluded, but he had this confusion.
In another version of this hadith, Zayd argues for the fact that the wives are not included among the Ahl al-Bayt by saying: I swear by God, a wife lives with her husband for a period of time and then she may get divorced and return to her own father and family.
In this way, Zayd wanted to suggest that someone’s wife is considered as the household of her own parents. They may go back to their home. The household of the Prophet are only those who are from the same root and origin as the Prophet and those who are prohibited to take charity after the Prophet.
There are also traditions about the meaning of Qurba (near ones) which has been mentioned several times in the Qur’an. For example, according to the verse 42:23, the Prophet did not ask any payment in return for his teachings from the people. He only wanted the people to love his Qurba for their own benefit.
So who are the Qurba? Zamakhshari, a great Sunni scholar and exegete of the Qur’an, says that when this verse was revealed, the Prophet was asked who was meant by this verse, and to whom all have to be respectful. The Prophet replied: “Ali, Fatimah, and their two sons.”14

The scientific authority of the Ahl al-Bayt?
The authority of the Ahl al-Bayt can be studied in two levels. The first regards the permissibility of referring to Ahl al-Bayt in order to understand Islam. Are the Ahl al-Bayt a reliable source? In other words, were they sound proofs (hujjah) for understanding Islam? The second raises the argument as to whether it is necessary to refer to the Ahl al-Bayt.

1) Permissibility of referring to the Ahl al-Bayt
According to the Sunni school of thought, all the companions of the Prophet were proofs as they quoted him to have said, “My companions are like stars; whomsoever you follow, you will be guided.”
Of course, this raises a myriad of questions because it is believed that whoever was a companion of the Prophet must have been deeply knowledgeable and pure-hearted enough to be reliable. Thus, both knowledge and piety must be guaranteed for all companions of the Prophet.
Moreover, Sunni scholars normally define the term companion (sahabi) quite broadly: a companion is he who met the Prophet at least once while believing in him. In other words, if someone met the Prophet for five minutes or half an hour while having faith in him, he became a companion.
Thus, all Muslims who lived in Medina, traveled to Medina, performed the pilgrimage (hajj) or met the Prophet by chance were his companions. Furthermore, those hypocrites who lived in Medina and declared their submission to Islam while the Qur’an portrayed the disbelief they harbored in their hearts also fall under the definition of companion.
With such a broad definition, how can one believe that whoever met the Prophet and declared his submission be a companion? It is necessary to have guidelines that discern true companions from the immoral ones.
According to the Shi‘a scholars, a companion of the Prophet is someone who believed in the Prophet and his message; one who has met him and lived with him for a considerable period of time (not a mere hour or two). Sahabi in Arabic refers to a relation that has endured over a reasonably long period of time.
First, it is irrational to believe that a strong relationship has occurred between a person and the Prophet within a mere hour. The development of true friendship naturally occurs over a longer period of time.
Second, it is not guaranteed that all people who lived with the Prophet and labeled themselves Muslims were truly Muslims who believed in the Prophet, as verified in the Qur’an. Some troubled the Prophet i.e. building a mosque with the purpose of harming Islam (masjid dirar) and attempting to assassinate him.
It is understandable that there were true companions who fully submitted to Islam and loved the Prophet, but it does not guarantee that whoever lived with the Prophet and declared Islam is a reliable person. It is evident that many conflicts arose amongst the companions after the demise of Prophet.
On occasion, the caliphs punished some companions for the good and wrong committed. The companions accused each other and even killed one another. Hence, not all companions were reliable. Nonetheless, since Sunnis believed that all the companions were reliable, sound, and just, they cannot dispute the authority of the Ahl al-Bayt.
They must accept both in theory and practice that the Ahl al-Bayt were reliable sources as well. If they dispute their authority in practice, they must at least accept it in theory.

2) Necessity of referring to the Ahl al-Bayt
The Ahl al-Bayt cannot be compared with other companions of the Prophet. Imam Ali was not like tens of other companions. It is the duty of every Muslim to refer to the Ahl al-Bayt. It is not merely because these people were close to the Prophet, or were members of his household who lived with him, though these are true.
It is because we have very clear instructions from the Prophet asking us to refer to them. And this is why it is an important aspect of Imamate.
It is not very helpful in this day and age to dispute with our Sunni brothers about who was supposed to be the first caliph, though it is an important historical discussion. Even more important is discussing who the most legitimate successor in presenting Islam was.
Even if we suppose that Abu Bakr was rightfully the first caliph and suppose that he was legitimately given this power, what still needs investigation is how to properly understand Islam in our day. And this is why we expect our Sunni brothers, those who believe in Abu Bakr as the legitimate successor, to refer to the Ahl al-Bayt.
Today we all must refer to the teachings of the Ahl al-Bayt in order to have a sound understanding of Islam.

Hadiths that indicate the authority of the Ahl al-Bayt

1) Hadith of Thaqalayn
The famous narration of the Prophet, the Hadith of Thaqalayn, is narrated in different versions by all Islamic schools of thought with regards to the Ahl al-Bayt. The Prophet may have mentioned it on different occasions due to its importance and to ensure that many can hear it: O People, I leave among you two precious things: the book of God and my household. As long as you hold on to them, you will not go astray.
In another version, the Prophet ordered a similar command: I leave among you two precious things. If you hold on to them, you will not go astray after me: the book of God, which is like a rope extended between the heaven and the earth, and my household. These two will not separate from each other until they reach me near the fountain of Kawthar on the Day of Judgment. Be alert with how you treat them after me.15
In the mid-1900s, Grand Ayatollah Borujerdi and the Shaykh of al- Azhar University, Mahmud Shaltut, established a Shi‘a-Sunni journal for Dar al-Taghrib Bayn al-Madhahib al-Islamiyyh called Risalat al-Islam published in Cairo.
In the first issue of this journal, an article by a Sunni scholar was published in which the author had used the hadith “I left you the Thaqalayn: the book of God and my sunnah” instead of ‘Itrati, my progeny, which is narrated by all Muslims. Upon reading the article, Ayatollah Borujerdi asked a scholar in Qum to collect all the Sunni references for “the Book of God and my progeny.”
As a result, a booklet containing 200 Sunni sources was produced. Ayatollah Borujerdi then sent this to the scholars at the al-Azhar in Cairo who published it. Thus, the hadith of Thaqalayn is an indisputable and well-established hadith.
Of course, even if we accept the version “the book of God and my Sunnah” which is narrated by only a few Sunni scholars, it will not cause any problem, because at best it can be taken equal to the version “the book of God and my household” and once the Prophet (s) never speaks in vain or in a contradictory way, the overall result would be that we need to refer to the book of God and the Sunnah of the Prophet in the way the household of the Prophet (s) have reported us.
If the Prophet in many cases said “Kitab Allah wa ‘Iitrati” and in some cases “Kitab Allah wa Sunnati” kitab Allah is the same in both hadiths, so sunnah and ‘Itra of the Prophet must be harmonious too. Thus, to be able to understand the Sunnah you must refer to the Ahl al-Bayt. One cannot believe in sunnah alone.
You need to refer to the Ahl al-Bayt to find the true sunnah. In any case, the following points can be inferred from the hadith of thaqalayn:
1) The book of Allah and the Ahl al-Bayt must be available until the end of this world. The Qur’an will always be available; thus, the Ahl al-Bayt must also continue. This is so because the Prophet said that if people appeal to both, they will never go astray until they meet him near the fountain of Kawthar. Thus, if the book of Allah or the Ahl al-Bayt (God forbid) is missing, how can we refer to them? Both must be available, not just one.
2) No one can say the book of God is enough by itself. When the Prophet wanted to dictate something while in his deathbed, he asked for something to write with and gave his reason (“So that you will not go astray”). The second caliph, Umar, was present, and according to Sunni sources, he said that the Prophet is not feeling well and does not have full control of what he is saying.
He then said, “The book of Allah is sufficient,” meaning that we do not need the instruction of the Prophet (s). However, according to the Qur’an itself, there must be someone as a teacher of the Qur’an. The Prophet (s) was the first one to teach the Qur’an to people and then this task was handed over to the Ahl al-Bayt and therefore the Prophet asked everyone to hold onto both the Qur’an and the Ahl al-Bayt.
The Ahl al-Bayt must be there to interpret the Qur’an because among the seventy-three sects (which emerged after the demise of the Prophet) exist various debates on the interpretation of the Qur’an. For example, in a dispute about the visibility of God, the Ash‘arites believed it is possible to see God with the physical eye.16
And they argued from the verse of the Qur’an which states,

“Some faces will be fresh on that day, looking at their Lord” (75:22-23).
Muslims such as the Shi‘a and Mu‘tazilites who disagree with the Ash‘arites argued from the Qur’an as well. Thus, there must be an interpreter of the Qur’an along with the Qur’an that can speak on behalf of the Qur’an to people.
3) The Ahl al-Bayt must be infallible. The Prophet’s mention of the Ahl al-Bayt and the Qur’an as two things that will never separate from each other proves their infallibility. If the Ahl al- Bayt made mistakes, that would mean they are separate from the Qur’an. People cannot simultaneously appeal to a perfect Qur’an and imperfect leaders.
Is it wise of the Prophet to ask us to unconditionally follow those who may make mistakes and sin? The Ahl al-Bayt will never go astray; this is why we can appeal to them. Moreover, we can be saved by following them. They must always be in line with the Qur’an, and since the Qur’an is the constant truth, the teachings of the Ahl al-Bayt must also be true.
Also, since the Qur’an is preserved by Allah until the end of the world, Ahl al-Bayt must have also been given a sort of continuity by Allah. This is why we believe that there must be a living member of the Ahl al-Bayt on this earth.
It should be noted that Sunnis accept whatever is there from the Ahl al-Bayt both in theory and practice, or at least in theory. Today, progress can be seen. For example, there are new rulings (fatwas) by our Sunni brothers about hajj, whether it is necessary to throw the stones only in the morning or it can be in the afternoon.
They had the view that it must be in the morning, and because it caused problems, they recently said it can be done in the afternoon according to the narration of Imam Baqir (a). So they have accepted a Shi‘a fatwa in this regard. There is no theoretical problem.

2) Hadith of Safinah
In a well-known hadith narrated by both Shi‘a and Sunni Muslims, the Prophet Muhammad (s) has likened his household to the ship, or safinah, of Prophet Noah: Be aware that surely the parable of my household among you is like the ship of Noah. Whoever embarked on the ship of Noah was saved, and however refused so was drowned.
This hadith directly refers to being spiritually guided and saved versus being drowned. According to the Qur’an, people have two lives: one is the physical life which we can examine through medical tests; the other is spiritual life i.e. the life of guidance and faith. The Prophets and their followers, such as the Imams and spiritual scholars, invite people to take care of their second life, not only the first one. The Qur’an says:

O you who have faith! Answer God and the Apostle when he summons you to that which will give you life… (8:24)
We believe that faith is a life for us, and if we lose it, we die spiritually, though we may be physically alive, and this causes to be spiritually deaf, dumb, and blind, leaving our hearts numb:

Deaf, dumb, and blind, they will not come back. (2:18)
According to the hadith of safinah, whoever refuses to appeal to the Ahl al-Bayt is spiritually destroyed. It is hopeless to be alive while having no leader, no direction in life.
There is another hadith in some Sunni sources like Al-Sawa‘iq al- Muhriqah by Ibn Hajar, in which after the Prophet likened his household to the ship of Noah, he likened them to the gate of Hittah as well.17 This was the gate that the Israelites were asked by God to enter:

And when We said, ‘Enter this town, and eat thereof freely whencesoever you wish, and enter prostrating at the gate, and say, “Relieve [us of the burden of our sins],’’ that We may forgive your iniquities, and soon We will enhance the virtuous.’ (2:58)

And when they were told, ‘Settle in this town and eat thereof whence you wish; and say, ‘‘Relieve [us of the burden of our sins],’’ and enter prostrating at the gate, that We may forgive your iniquities, and soon We shall enhance the virtuous.’ (7:161)
Whoever entered the gate was forgiven and whoever refused to enter was punished. Similarly, those who follow the Ahl al-Bayt receive God’s mercy and forgiveness and those who arrogantly refuse to do so will be punished by God.
In yet another hadith the Prophet likens his household to stars. Stars are not just to lighten the sky or beautify it. The fixed stars are a source for guidance for those who travel in the oceans and deserts.
The Prophet likened the Ahl al-Bayt to these stars, since they are guides that save people from going astray or from conflict. The hadith goes on saying that if a group of Arabs disagree with the Ahl al-Bayt, they will suffer with disagreements that bring about disunity and result in being a part of the party of Satan. In this way, the Prophet disapproves those who disputed against the Ahl al- Bayt.
Thus, referring to the Ahl al-Bayt to understand Islam is not optional; it is a must. These hadiths, namely the hadith of Thaqalayn, the hadith of Safinah, the hadith of Hittah and the hadith of stars are some of the very well-known ones found in Sunni references. Similar narrations indicating the necessity of referring to the Ahl al-Bayt are found in Shi‘a collections of hadith.

Conclusion
Being one of the five principles of Shi’a Islam, the concept of Imamate holds such an importance that being oblivious of the Imam of our age is likened to a person who died before Islam. The different views among Muslim theologians concerning this subject relate to its significance, the Imam’s role, and the characteristics the leader must hold.
The Shi’a believe that a successor to the Prophet must continue his leadership as a teacher, a judge, and a political leader. Bearing this in mind, an Imam must be knowledgeable, pious, and capable of leadership.
Indeed, when recognizing the status of Ahl al-Bayt as those to whom we appeal to alongside the Qur’an, we see that those revered infallibles are none other than Imam Ali, Fatima, and their two sons, Hasan and Husein. Upon reading several hadiths concerning this subject, the Prophet clearly instructed people to refer to them as a reliable and necessary source in understanding Islam.
1. Associate Professor at the Imam Khomeini Education & research Intitute, Qum.
2. ‘Allamah Majlisi in Bihar al-Anwar, vol. 8, p. 368 recognizes this hadith as mutawatir for both Sunni and Shi‘a. This means that this hadith has been so frequently mentioned in every generation of the narrators of hadith that leaves no chance for anyone to question its authenticity.
3. For example, see Al-Kafi, vol. 1, p. 372, where Imam Baqir (a) is quoted as saying:

.
Elsewhere (ibid. p. 376) he quotes the Prophet’s from Imam Sadiq (a):

.
4. The principle of promise and threat indicates that Allah (swt) keeps His promises of rewarding good people and punishing criminals.
5. Re ‘enjoining good and forbidding evil’, they had the idea that there are stages: first, you should like good and dislike evil in your heart; second, you must tell the wrongdoer to discontinue sinning and perform his duties; third, if it does not work, steps are to be taken to discontinue the sin (i.e. if your child does not pray, you must take practical measures to make sure he does so). If needed practical measure including usage of force must be taken. To stop a crime or to defend one’s honour one may need to get involved in resistance and fight (jihad), and be prepared for sacrificing one’s life.
6. There has been some controversy among Muslims about those who have committed a great sin. Some consider them as Muslims; others consider them to be disbelievers (kuffar). The Mu’tazilites believe they are in between Islam and disbelief.
7. Abu Sufyan was the leading man of the Quraysh in Mecca and staunch opponent of Prophet Muhammad (s).
8. For a detailed list of Sunni sources, in which this saying is reported, see e.g. Sultan al-Wa‘izin Shirazi, Peshawar Nights, “Evidence Regarding Umar's Saying ‘Had Ali Not Been There, Umar Would Have Been Ruined.’”
For example, he quotes from the great theologian, Ganji Shafi'i, in Chapter 57, of his Kifayat al-Talib Fi Manaqib Ali ibn Abi Talib, after narrating some authentic hadith, reports from Hudhaifah ibn Yaman that "One day ‘Umar met him and asked him, 'What was your condition when you awoke in the morning?' Hudhaifa said, 'I rose in the morning hating the Truth, liking fitnah, bearing witness to the thing unseen; learning by heart the uncreated, reciting salutations without being in the state of ritual purity, and knowing that, what is for me on the earth is not for Allah in the Sky.' ‘Umar was infuriated by these remarks and intended to punish Hudhaifah when Ali came in. He noticed the signs of rage on ‘Umar's face and asked why he was so angry.
‘Umar told him, and Ali said: 'There is nothing serious about this remark: what Hudhaifah said was correct. Truth means death, which he detests; fitnah means wealth and children, which he likes; and when he says he bears witness to what he has not seen, this means that he testifies to the oneness of Allah, death, the Day of Judgement, Paradise, Hell, the bridge over it named Sirat, none of which he has seen. When he says he learns by heart what is uncreated, this refers to the Holy Qur'an; when he says that he recites salutations without ablution, this refers to reciting salutations on the Prophet of Allah, which is permissible without ablution; when he says he has for himself on earth what is not for Allah in the sky, this refers to his wife, as He has no wife or children.'
‘Umar then said, ' ‘Umar would have been lost had Ali not arrived.'" Ganji Shafi'i says that ‘Umar's statement is verified according to reports of most of the narrators of hadith. The author of Manaqib says that Caliph ‘Umar repeatedly said: "O Abu'l-Hasan! (Ali). I would not be a part of a community without you." He also said: "Women are unable to give birth to a child like Ali."
Muhammad Bin Talhah Shafi'i in his Matalibu's-Su'ul and Sheikh Sulayman Balkhi Hanafi in Yanabiu‘ al-Mawaddah, Chapter 14, narrating from Tirmidhi, record a detailed report from Ibn Abbas at the end of which he says, "The companions of the Prophet used to seek religious judgments from Ali, and they accepted his decisions. Thus, ‘Umar Bin Khattab said on various occasions, 'If it were not for Ali, ‘Umar would have been ruined." …Even Ibn Hajar Makki in Chapter III of Sawa‘iq Muhriqaah, reporting from Ibn Sa‘d, quotes ‘Umar as saying, "I seek Allah's help in deciding those difficult problems for which Abu-l- Hasan (Ali) is not available."
9. Apart from a small group called Nawasib (the plural form of nasibi), all Muslims love the Ahl al-Bayt. However, there are two problems: Non-Shi‘a love the Ahl al-Bayt, but they do not necessarily take Islam from them. Secondly, non-Shi‘a believe that Ahl al-Bayt includes Imam Ali, Lady Fatimah, Imam Hasan and Imam Husayn, but they extend it to other relatives of the Prophet as well.
10. Sahih of Muslim, Vol. 4, p. 1883, No. 2424. (Kitab Fada’il al-Sahabah, Bab Fada’il Ahlul Bayt, Sakhr serial no. 4450)
11. Red camels were considered very valuable at the time.
12. Sahih of Muslim, Vol. 4, p. 1871, no. 2408. (Kitab Fada’il al-Sahabah, Sakhr serial No. 4420).
13. Musnad of Imam Ahmad b. Hanbal, Sakhr serial no. 13231. See also Sunan of al-Tirmidhi, Sakhr serial no. 3130.
14. Al-Kashshaf by Zamakhshari, Commentary on the verse 42:23, Vol. 4, p. 220.
15. These hadiths are mentioned in many Sunni sources. For example, see Sahih of Muslim, vol. 8, p. 25, number 2408, Musnad, No. 10720, Sunan of Darimi, vol. 2, p. 432, Sahih of Tirmidhi, vol. 5, p. 6432, No. 3788. It is also found in other books, such as Usd al-Ghabah (the Lions of the Forest) on the biographies of the Companions of the Prophet, Al-Sunan al-Kubra and Kanz al-‘Ummal.
16. Ash’arites: followers of a theology founded by Abu al-Hasan al-Ash’ari in the mid-900s
17. For a Shi‘a source, one may refer to Bihar al-Anwar, vol. 23, p. 105, where ‘Allamah Majlisi cites the following hadith from the Bisharat al-Mustafa: