First of all, one must note that: 1- The imams’ names have been explicitly mentioned in the Prophet’s sayings, especially Imam Ali’s name in which the Holy Prophet of Islam has in many different events, clearly stated that Imam Ali is his successor and the  religious authority after him. For example, in the wake of Prophet Muhammad’s prophethood, when he was ordered by Allah to invite his tribe, family, and relatives to Islam, he declared: “The first person to believe in me (answer my call to Islam) will be my wasiyy, minister, and successor.” The only person to answer him was Imam Ali (a.s.). In the end, when no one answered the Prophet other than Ali (a.s.), he said: “After me, you (Ali) are my wasiyy, minister and successor.”[1] Another example is the famous hadith of Ghadir in which the Prophet clearly stated that: “Whosoever I am his Mowla, Ali is his Mowla.”[2] Also in the hadith of Manzilah, the Prophet states that: “You (Ali (a.s.)) are in comparison with me, like Harun compared with Musa, the only difference (between us and them) is that there is no prophet after me.”[3] The hadiths of the holy Prophet (p.b.u.h.) regarding the fact that Imam Ali (a.s.) will take his place are mostly Mutawatir (meaning that there is no doubt that the hadith has been said by the prophet because the number of narrators is so high that one becomes sure that it is impossible for the hadith to be an unauthentic one) and this fact has been pointed to in both Sunni and Shia books.[4] In yet another hadith, the Prophet (p.b.u.h.) names all of the imams after him for Jaber-ibn-Abdillah-al-Ansari, from Imam Ali until the twelfth and final imam meaning Imam Mahdi (a.s.).[5]

So one should be aware that although the imams’ names haven’t been explicitly stated in the Quran, yet the holy Prophet, whose words are all true and come from Wahy (divine inspiration)[6], has clearly expressed their names and emphasized on their being imams after him.

2- Imam Ali’s Wilayah (religious authority) has been pointed out in the Quran even though his name hasn’t been explicitly mentioned. Both Shia and Sunni commentators of the Quran admit that verse 55 of surah Ma’idah has been revealed regarding Imam Ali (a.s.) and that he is the only one meant by it.[7] “Only Allah is your waliyy and His apostle and those who believe - those who establish salat and give charity while bowing (in rokoo’).”

Given the fact that in Islam there is no ruling saying that giving charity while in rokoo’ (bowing in prayer) is preferred as mustahabb or wajib, one can easily conclude that this verse is pointing to an event that occurred only once. This verse is speaking of the time in which Imam Ali was praying in the masjid. When he went down to rokoo’, a beggar came up to him asking for help, Imam Ali pointed to his finger and the beggar approached him, took off the imam’s ring and left.[8] Thus, the verse is saying that religious authority and supervision of the Islamic ummah are solely[9] for Allah, His messenger and Imam Ali (a.s.), and other than them, no one has any authority.

So, till now we have concluded that the imams’ names have been mentioned by the Prophet (p.b.u.h.) and Imam Ali’s wilayah has clearly been pointed to in the Quran, such that an unprejudiced and unbiased researcher really searching for the truth, can easily reach the conclusion that the Prophet’s (p.b.u.h.) standpoint on those succeeding him, was that Imam Ali (a.s.) and his children are to succeed him after his passing away. But why haven’t Imam Ali and the other imam’s names been explicitly mentioned in the Quran? There can be two reasons behind this issue:

1- “The Quran usually speaks in a very general way and mostly teaches us principles, ways and methods (instead of getting very specific) as it has regarding the osool (pillars)and foroo’ (branches) of Islam.” This is what Imam Sadeq (a.s.) has said.[10] He goes on to give us three examples:  a) Salat. The Quran has been general regarding salat; not being specific about how long it is supposed to be and how it is supposed to be performed. On the other hand, the Prophet of Islam (p.b.u.h.) has clearly illustrated how to perform it for us and how many rak’ats each prayer should be. b) Zakat. In the Quran, zakat has only been mentioned as an Islamic ruling. It was the Prophet who expressed which things have zakat and what the criteria for zakat becoming wajib for each one is.

c) Hajj. The Quran says that Hajj is wajib and no more, but the Prophet has explained how it is supposed to be performed.[11]

Therefore, it is wrong to expect to be able to find every detail in the Quran. So it is a big mistake not to follow the imams just because of the fact that none of their names have come in the Quran. That’s why no one says that noon prayers (which are 4 rak’ats) have to be prayed 2 rak’ats just because the Quran hasn’t mentioned how many rak’ats  each prayer is.

2- In issues like this, in which there are big chances that others will disagree, it is much better for the Quran to express the truth implicitly rather than explicitly, otherwise there is a high possibility that they will end up denying the Quran as a whole. It’s very obvious that such a problem isn’t to the benefit of the Muslim ummah. Of course, the Quran says: “Surely we have revealed the Reminder (the Quran), and We will most surely be its guardian”[12], but one should remember that one of the ways of protecting the Quran and not letting others falsify or change it, is for it to speak in a way that others (such as the hypocrites who show that they are Muslims on the outside even though they aren’t within) don’t get sensitive and provoked.  In this way, the high respect and value of the Quran will be kept, and certain individuals won’t think of changing or falsifying it in a way that will comply with their personal desires and wicked goals or just because they disagree with something.[13]

Shahid Ayatollah Motahhari answers this question in the following way. He says: “The answer to the question that why hasn’t Imam Ali’s khilafah and imamah been mentioned in the Quran, is that 1- The Quran usually expresses general laws. 2- The Holy Prophet (p.b.u.h.) or Allah (s.w.t.) didn’t want such an issue in which people are sensitive about and prefer their own desires (to what Islam wants), to be presented explicitly, and although it wasn’t, people still went against it and falsely interpreted the Prophet’s sayings to their own benefit. In other words even if the Quran had clearly stated that Ali (a.s.) is successor to the Prophet they still would have found a way around it. The holy Prophet (p.b.u.h.) said: "ذا علی مولاه" (Ali is his Mawla). How much more clear can one get? (Yet they interpreted what he said falsely and according to their will.)Yet there is a big difference between ignoring what the Prophet (p.b.u.h.) has said after him passing away regardless of all of its clarity and ignoring what the Quran has been completely clear about one day after his demise. That is why I have narrated in my book “Khilafah and Wilayah” that once during Imam Ali’s reign, a Jew wanted to attack and criticize the Muslim ummah for undesirable events that took place in the beginning of Islam. He told Imam Ali (a.s.) (and of course what he said really was a negative point) that you (the Muslim ummah) started quarreling over your prophet even before completely burying him after his death. Imam Ali answered: We argued about what he had instructed, not over the Prophet himself, but you (meaning the Jews) disregarded the most important principle of your religion which is tawhid (oneness of God), and asked your prophet to build an idol for you to worship. So there is a big difference between you and us; we didn’t argue about our prophet, we argued about what the interpretation of his saying was (and what he wanted us to do after his death). These two vary tremendously. (Motahhari goes on to say that) there is a big difference between saying that the people back then had misunderstood what the Prophet had said and saying that the Muslims back then rejected what the Quran had clearly stated or had falsified it.[14]

So one can say that the main reason behind not mentioning the names of the imams, or at least Imam Ali’s name, is the protection of the Quran from falsification and change, and that is why the verses of tathir[15], tabligh[16], and wilayah[17] are all located between verses that are either talking about the Prophet’s wives, different Islamic rulings, or not being friends with The People of the Book (ahlul-kitab), which all have nothing to do with the religious authority of the imams and Imam Ali (a.s.), yet the fair and unbiased researcher can with the least consideration tell that this part of the verse is separate from the verses before and after it and is located there for a certain reason.[18][19]

For further information, see “The Quran and Imam Ali (a.s.)”, question 324 (website:1817).