The significant status of the People of the Household (Ahlul Bayt) of the Holy Prophet (S) had been continuously emphasised by the Holy Prophet (S) himself during his life time. There are many Ahádith (traditions) to this effect.
The most renowned Hadith is that which is known as "Thaqalayn" - "Two 'Heavy' things". The Holy Prophet (S) said, "I leave behind two heavy things for you - The Holy Qur'án and my Ahlul Bayt; if you hold fast unto them, you shall never go astray for they will never separate until they come to me together on the Day of Resurrection".
This significance of the Ahlul Bayt has also been mentioned in the Holy Qur'án several times. They are specifically mentioned in verse 33 of Súrah al-Ahzáb, which is known as Áyat ut Tathír, literally meaning "the Verse of Purification".
We narrate Hadith-e-Kisá (The event of the Cloak) quite regularly whenever we gather for a Majlis, whether in large numbers or small. The event is said to have taken place at the residence of Bibi Fátimah (A).
The narration states that the Holy Prophet (S) came to the house of his daughter and requested for a cloak and then lay down to rest. His grandsons, Imám Hasan (A) and Imám Husain (A) came and joined him under the cloak. Thereafter, Imám 'Ali (A) and Bibi Fátimah (A) also came under the cloak.
Bibi Fátimah (A) narrates that when they were all assembled under the cloak, Jibrá-íl (A) came to the Holy Prophet (S) and conveyed to him the verse which reads:
Verily, Alláh wishes to drive away all evils from you, O Ahlul Bayt, and cleanse you thoroughly. (al-Ahzáb, 33:33)
At this time, Umme Salma, a virtuous wife of the Holy Prophet (S), asked if she could join them under the cloak and be included in the Ahlul Bayt. The Holy Prophet (S) replied : "You are a good woman but it is better that you stay where you are".
As a reference to the event of the cloak, the group assembled under the cloak have been referred to as "Panjatan Pák" or "Holy group of Five".
This narration of where the verse was revealed has been recorded in both the Shi'ah and Sunni history books. Two important Sunni references are "Sahih" of Muslim bin Hajjáj, and "Musnad" of Ahmed ibn Hanbal.
At the end of Hadith-e-Kisá, it is narrated that Imám 'Ali (A) asked the Holy Prophet (S) as to the significance of the gathering under the cloak. The Holy Prophet (S) replied that any group that mentions the event in their gathering, the angels will seek forgiveness for them until they disperse. The Holy Prophet (S) also said that anyone who has a dire need or is in sorrow will have his prayer answered by the blessings of the narration of the event of the cloak.
When studying the Áyah of Tathir, one will undoubtedly note that the verse begins with addressing the wives of the Holy Prophet (S). Hence, some argue that the people referred to in this verse as Ahlul Bayt are the wives, and not the children of the Holy Prophet (S). To this there is a very simple and convincing answer.
The mode of address used in addressing the wives is the feminine plural mode. Hence, in the words "Qarna fi Buyútikunna.." - the nún at the end denotes feminine plural address exclusively to the wives of the Holy Prophet (S). Yet, when we come to the part of Ahlul Bayt, the verse switches to a different mode of address - "'Ankum.. Yutahhirakum.." This mode of address is used either for exclusive male plural or male and female mixed plural. Hence the verse changes to addressing a different group of people in a discourse that is overall being addressed to another group. The verse is addressing the wives of the Holy Prophet (S), except in this small part of the verse! In this last part, the address is directed to the Household of the Holy Prophet (S).