"Ahl al-Bayt" literally means people of the house and it refers to the family or children of a person. In Islamic terminology, it refers to the family of the Prophet Muhammad (P.B.U.H.) What is the basis of the importance given to the Ahlul Bayt of the Prophet? Is there anything about it in the Qur'an and the sayings of the Prophet? Or is this an old Arab tribal concept with no basis in Islamic sources? The Qur'an and the hadith have a lot to say about the Ahlul Bayt. However, before we even go to the Qur'an, a clarification on the concept of Ahlul Bayt is necessary.
The term "family of the prophet" can be applied on three kinds of relationships: • Those who are related to the prophet by blood or marriage ties only. • Those who are related to the prophet by soul and spirit only. • Those who are related to the prophet by blood or marriage ties as well as by soul and spirit. When the Qur'an or the Prophet uses the term "Ahlul Bayt", it could not be the first or the second group.
The first group is only physically related to the Prophet but not spiritually, like the son of Prophet Nûh or the wife of Prophet Lût or Abu Lahab, the Prophet's uncle. Allah clearly says to Prophet Nûh about his son: "Innahu laysa min ahlik - He is not of your family." (11:45-46) That is, he is not one of your spiritual family; he is only physically related to you. Lût's wife and the Prophet's uncle, Abu Lahab, both are counted as people of the Hell-Fire. The second category is considered "Ahlul Bayt" only in a metaphorical sense, not in the real meaning; for example, Salman al-Farsi about whom the Prophet said, "Salman is from us, the Ahlul Bayt." This leaves us with the third group.
Who Are the "Ahlul Bayt"? Many people were related to the Prophet both by blood and marriage as well as by soul and spirit. But the term "Ahlul Bayt" as used by the Qur'an and the Prophet does not apply to all of them. We see that Prophet Muhammad (P.B.U.H) clearly applied the Qur'anic term "Ahlul Bayt" to four people: Fatima, 'Ali, Hassan and Husayn (peace be upon them all).
The first verse (33:33) is the verse of purification (tathir): "Verily Allah intends to keep away the abomination from you, O the Ahlul Bayt, and purify you a thorough purification." No Muslim would question the inclusion of Fatima, 'Ali, Hassan and Husayn in the "Ahlul Bayt". The disagreement arises in the inclusion of the wives and other Hashimite relatives of the Prophet among the "Ahlul Bayt". For example, during our time, a book has been published in Saudi Arabia entitled as 'Allimu Awladakum Hubb Al-i Bayti 'n-Nabi (Teach Your Children the Love of the Family of the Prophet) by Dr. Muhammad 'Abduh Yamani in 1991. The order in which Yamani talks about the Prophet's family is very interesting: he first talks about Khadija, then Fatima, 'Ali, Hasan, Husayn, Zaynu 'l-'Abidyn, and then ends with the other wives of the Prophet.
Wilfred Madelung makes the following observation on the verse of purification: "Who are the 'people of the house' here? The pronoun referring to them is in the masculine plural, while the preceding part of the verse is in the feminine plural. This change of gender has evidently contributed to the birth of various accounts of a legendary character, attaching the latter part of the verse to the five People of the Mantle (ahl al-kisa'): Muhammad, 'Ali, Fatima, Hasan and Husayn. In spite of the obvious Shi'ite significance, the great majority of the reports quoted by al-Tabari in his commentary on this verse support this interpretation."
From the many reports that the Sunni sources narrated, here I am just quoting one as an example. Abu Sa'id al-Khudari quotes Umm Salama, the wife of the Prophet in whose house the incident of Kisa' took place. She says: Jibra'il came with the verse of purification; the Prophet called Hasan, Husayn, Fatima and 'Ali, and he gathered them together and covered them with the mantle. Then he said, "O Allah, these are my Ahlul Bayt, so 'keep away the abomination from the Ahlul Bayt, and purify them thoroughly.'" Umm Salama (may Allah be pleased with her) said, "Am I with them, O Apostle of Allah?" The Prophet said, "You stay in your place, and you are virtuous."
Since this verse is situated right in the midst of the verses addressed to the wives of the Prophet, some Sunnis use its position to include the wives in the "Ahlul Bayt". But the problem with their interpretation is the difference in the pronouns: the sentences before and after the verse of purification have feminine plural pronouns whereas the statement itself has the masculine plural pronouns. This is internal evidence that the statement of purification was an independent verse that was revealed on its own in a different event unrelated to the wives.
In spite of the great majority of reports by Sunnis supporting the view that this part of the verse was a separate revelation that was later attached to the rest, Madelung has difficulty in accepting it as such. In his interpretation, he has tried to apply the term 'Ahlul Bayt' primarily to the Bani Hashim and then, in the second place, to the wives. But he has failed to explain the gender difference in the pronouns used in the whole passage.
The Shi'ite and Sunni reports clearly apply the term "Ahlul Bayt" in the statement of purification to the Ahlul Kisa', excluding the wives of the Prophet. And the gender difference in the pronouns was to show the contrast between the "Ahlul Bayt" and the wives. In words of Mirza Mahdi Puya, "While the address in the beginning of the verse is in the feminine gender - there is the transition here in the address from the feminine to the masculine gender. While referring to the consorts of the Holy Prophet, the pronouns also are consistently feminine. For a mixed assembly of men and women, generally the masculine gender is used. This transition in the grammatical use of the language, makes it quite obvious that this clause is quite a different matter used for a different group other than the previous one, and has been suitably placed here to show a comparative position of the Ahlu 'l-bayt in contrast to the wives of the Holy Prophet." Another important verse of the Qur'an that talks about the Ahlul Bayt is 42:23 in which Allah, subhanahu wa ta'ala, says: "(O Muhammad) Say, 'I do not ask for any reward for this (bringing of Allah's message) except the love for the near kinship.'"
The fact that this verse was revealed concerning the Ahlul Bayt, the family of the Prophet, is beyond any doubt. Imam Shafi'i, the founder of the Sunni Shafi'i School of law, has explained the meaning of this verse in a poem:
O Ahlul Bayt of the Messenger of Allah, your love, Is a duty from All?h, mentioned in the Qur'an. In your honour, it is sufficient that one's prayer, Is incomplete without praying for blessings on you. The Sunni polemicists have tried to reject the Shi'a point of view by the following arguments: (1) This verse was revealed in Mecca when Hasan and Husayn were not yet born, so how could it be applied on the Ahlul Bayt in the sense of Ahlul Kisa'? (2) Since it was revealed in Mecca, it is addressing the Quraysh by asking them 'to love Muhammad because he is from their kinship.' (3) Some say that it refers to all the Hashimites, and not just the Ahlul Bayt in the Shi'i definition. First of all, the commentators of the Qur'an overwhelmingly state that even though chapter 42 is a Makkan surah, its verses 23-25, 27 were revealed in Medina. This makes the first and second arguments mentioned above baseless.
Secondly, the commandment asking for "love of the kinship of the Prophet" cannot apply to all of his kin because there were good as well as evil people among them; and so one has to restrict the import of this verse to those who were physically as well as spiritually connected to the Prophet. And no one can argue that 'Ali, Fatimah, Hasan, and Husayn were not among those who were physically as well as spiritually related to the Prophet, even though he might extend this title to other members of Hashimite.
Finally, there are many reports in Sunni sources in which the Prophet applies this verse to the Ahlu 'l-Kisa'. For example, when this verse was revealed, the people asked the Prophet: "Who are these near kin of yours whose love is obligatory upon us?" He replied, "'Ali, Fatima, and their two sons." He repeated this three times.
Footnotes:  Published by Daru 'l-Qiblah li 'th-Thaqafati 'l-Islamiyya in Jeddah.  Madelung, The Succession to Muhammad, p. 14-15.  As-Suyûti, ad-Durru 'l-Manthûr, vol. 5, p. 197. Also see at-Tabari, Jami'u 'l-Bayan, vol. 7, p. 22; Muhibbu 'd-Din at-Tabari al-Makki, Dhakhairu 'l-'Uqba, p. 55-60.  See note no. 1857 (p. 1261) in the Holy Qur'an, translated by S.V. Mir Ahmad Ali. For other quotation from Sunni sources on this verse and its application to the Prophet, Fatima, 'Ali, Hasan and Husayn (peace be upon them all), see SSA Rizvi, Imamate: the Vicegerency of the Prophet (Tehran: WOFIS, 1985) p. 49-54; Sayyid Murtaza al-'Askari, Verse of Purification (Bombay: World Islamic Network, 1998) which is an incomplete translation of his Hadithu 'l-Kisa' fi Masadiri 'l-Madrasatayn (Tehran: Nashr Tawhid, 1997). For a comprehensive discussion on this verse and its relation to the Ahlul Bayt, see Syed Ja'far Murtaza al-'Amili, Ahlu 'l-Bayt fi Ayati 't-Tathir (Beirut: Daru 'l-Amar li 'th-Thaqafah, 1993).  Muhammad bin Idris ash-Shafi'?, Diwanu 'sh-Shafi'i, ed. Muhammad al-Khafiji (Jeddah: Maktabah Dar Hira', n.d.) p. 106.  For an exhausting discussion on this verse of "love the kinship", see Ja'far as-Subhani, Mafahimu 'l-Qur'an, vol. 4 (Beirut: Daru 'l-Azwa', 1986) pp. 17-72.