The term Ahl signifies the members of a household of a man, including his fellow tribesmen, kin, relatives, wife or wives, children and all those who share a family background, religion, housing, city and country with him.
Bayt refers to habitation and dwelling, whether tented or built. It can also be roughly translated as “household”. The Ahl-Al-Bayt of a person refers to his family members and all those who live in his house. Ahlul Bayt is the polite form of addressing the members and wife of the family.

In the Qur’an
In Verse 33:33 of the Holy Quran, there is a change to masculinity of the Arabic text ‘ankom’ which symbolises the ‘Ahlul Bayt’, it is also believed, that as this specific verse came down, it was when the prophet Muhammed (s) had been sitting with the members of Ahlul Bayt ( Ali, Fatima, Hassan and Hussein). According to some interpretations, the Qur’an also implicitly refers to Ahl al-Bayt in 42:23 using the term al-qurbā.
There is a consensus amongst Sunni and Shi’a Muslims that the “Ahl al-Kisa” hadith refers specifically to Ali, Fatimah, Hasan and Husayn. Mention of the Ahl al-Bayt, Muhammad’s household, is present in a verse of the Qur’an as follows ;
O wives of the Prophet! you are not like any other of the women; If you will be on your guard, then be not soft in (your) speech, lest he in whose heart is a disease yearn; and speak a good word.
And stay in your houses and do not display your finery like the displaying of the ignorance of yore; and keep up prayer, and pay the poor-rate, and obey Allah and His Messenger. Allah only desires to keep away the uncleanness from you, O people of the House! and to purify you a (thorough) purifying.
And keep to mind what is recited in your houses of the communications of Allah and the wisdom; surely Allah is Knower of subtleties, Aware.
—Sura Al-Ahzab (33), ayat 32-34.
The precise definition of the term in this verse has been subject to varying interpretations. In one tradition, according to which Muhammad’s (S) companion Salman al-Farsi is included as a member, it is used to distinguish from the muhajirun (Muslim emigrants from Mecca) and ansar (Medinan converts to Islam).
Further members of the household, according to the Sunni perspective, include Ali, Fatimah, Hasan and Husayn, who are mentioned in the tradition of the mantle.. Thus, according to the Encyclopaedia of Islam, “[t]he current orthodox view is based on a harmonizing opinion, according to which the term ahl bayt includes the ahl al-ʿabāʾ, i.e. the Prophet, ʿAlī, Fāṭima, al-Ḥasan and al-Ḥussain, According to Laura Veccia Vaglieri in Encyclopaedia of Islam “there is a story narrated in many traditions according to which Muḥammad sheltered under his cloak, in varying circumstances including the Mubahala, his grandchildren Ḥasan and Hussein, his daughter Fatimah and his son-in-law Ali; and therefore it is these five who are given the title Ahl al-Kisa or “People of the Mantle”. Some have attempted to add Muḥammad’s wives to the list; however, the number of the privileged is limited to these five.

Other interpretations include the family of Ali, as well as the families of Muhammad’s relatives such as Aqeel, Ja’far, and ‘Abbas ibn ‘Abd al-Muttalib|al-Abbas. Early Islamic jurists Malik ibn Anas and Abū Ḥanīfa included the clan of Banu Hashim within the definition, while al-Shafi’i included the whole of Banu Muttalib.[1]

In Shia thought, the household is limited to Muhammad, Fatimah, Ali, Hasan, Husayn, and their descendants (altogether known as the Ahl al-Kisa); as per their deduction from the tradition of the mantle. They interpret the change in pronoun in the Qur’anic verse as showing that only the aforementioned members constitute Ahl al-Bayt.[1] Madelung writes that “[t]his change of gender has inevitably 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.”[10] Shias view these individuals as infallible and sinless Imams and regard devotion to them as an essential part of the religion.

Shia Muslims also support this claim with a hadith mentioned in the Sunni Ṣaḥīḥ collection. Many Sunni scholars remark that the verse of purification was revealed concerning five people: Muhammad, Ali, Fatimah, Hasan and Husayn.

‘A’isha reported that Allah’s Apostle (may peace be upon him) went out one morning wearing a striped cloak of the black camel’s hair that there came Hasan b. ‘Ali. He wrapped him under it, then came Husain and he wrapped him under it along with the other one (Hasan). Then came Fatima and he took her under it, then came ‘Ali and he also took him under it and then said: Allah only desires to take away any uncleanliness from you, O people of the household, and purify you (thorough purifying)

The most authentic hadith among Shias is attributed to Fatimah Zehra (s) narrated by Hazrat Jabir Ibne Abdullah Ansari who is most respected by both Shias and Ahle Sunnah wal Jama’a .Ansari (r a ) narrates that when all the five came under the canopy of the kisa e Yamani , then the Rasool e Kareem (s) supplecated ” Ya Allah these are my Ahlebayt , keep all kind of rijs away from them ” and then this portion of Aya e tatheer ” innama yureedullah …..”was revealed by the Angel Jibraeil (A S ).

The tradition about this hadith goes from different sources to Fatimah (s), the daughter of Muhammad. She narrated that once her father visited her home, he had fever and was not feeling well, he asked for a Yemeni cloak which Fatimah (s) brought to him and folded it around him. Later he was joined in that Yemeni cloak by his grandsons Hasan (a) and Hussein (a), who were followed by their father Ali ibn Abi Talib (a), who was cousin and son-in-law of Muhammad (s). Finally Fatimah (s) asked the permission to enter that cloak. When all five of them joined together under the cloak, Muhammad narrated the Qur’anic verse 33:33 to those under the cloak that all five of them are chosen ones, and he further stated that he wants God to keep all impurities out of reach and away from all of us. Muhammad then prayed to God to declare all five of them as his Ahlul Bayt and keep away the Najasat (impurities). God, at that request immediately sent Gabriel (Jibral) to
reveal to Muhammad that all the five under the cloak are dearest and closest to God and they are Taher (“purest of the pure”) without any traces of impurities.
It is also reported from Umme Salmah (s) the mother of believer in whose house the Ayat was revealed that she asked can she also come inside the canopy of kissa , the rasool e kareem (s) praised her, gave her great tidings but said you are well where you are . Now if that wife was not included in the privillaged five there is absolutely no question of any other wives included in the Ahlebait ‘ Further it must be noted that in the same verse there was strict instructions ” not to go out of the house ” which other mothers of believers followed so strictly that they did not go out even to perform Hajj , while one of the wife not only went out of the house but she waged a war with none else but the husband of her own step daughter who at that time was undisputed Khalifa e Rashidoon . The Shias regard him & justifiably too as divinely appointed bila fasl .

Now the Ummah have every justification to finally believe that only the blood relation progeny are the only one entitled to be included in the Ahlebait e Rasool (saawaws) and the wives are outside the perview of the Ayat e Taharat and worthy of great reverence & respect .The absence of Sahabah and the mother of believers from the team MOBAHILAH is further proof despite Allah’s open command for both the parties to bring your men, women and children but while all the wives and sahabas were very much available , rather keen to be waiting but the Rasool e Kareem took among his NAFS , as Ali Ibne Abi Talib (a) , among his women only his daughter Fatima Zehra (s) and among his children, his two grandsons Hasan (a) and Husain (a)., Indeed these Panjatan Paak are only thoroughly purified .