Traditionally and literally, the "Ahl al-Bayt" or "the members of the household" and the family of a man are those who live as members in the small society of his house such as his wife, son, daughter, and servant living within the housing complex of the house owner.
Sometimes, the meaning of the Ahl al-Bayt is generalized to include close relatives such as father, mother, sister, children, uncle, father's sister, maternal aunt, and their children.
However, the meaning of "the Ahl al-Bayt (as)" of the Holy Prophet (S), expressed in the Holy Qur'an and ahadith, is not in line with the two preceding definitions. According to successive ahadith related through general and specific channels, "the Ahl al-Bayt" is a name granted as a gift to specially include the Holy Prophet (S) and the respectable ones, 'Ali (as), Fatimah (as), al-Hasan (as), and al-Husayn (as).
Therefore, on this basis, the other members of the Prophet's household and his relatives (although they are traditionally and literally considered as members of his household) are not covered by this definition.
Even Khadijah al-Kubra (as), who was the most respectable wife of the Holy Prophet (S) and the mother of Fatimah (as) and also Ibrahim, who was the consanguineous son of the Holy Prophet (S) and who had the greatest honor, are not included in "Ahl al-Bayt (as)" of the Holy Prophet (S).
Indeed, according to these and other ahadith, nine infallible Imams out of twelve infallible Imams, who are the sons and offsprings of Imam Husayn (as), are also included in the Ahl al-Bayt (as) of the Prophet (S). Therefore, the "Ahl al-Bayt (as)" are the fourteen infallible ones. Usually, the "Ahl al-Bayt (as)" of the Holy Prophet (S) refer to thirteen persons, who are the offspring of the Holy Prophet (S).
The Ahl al-Bayt of the Holy Prophet (S) are endowed with many virtues, excellent qualities, and unchallenging positions, the most important of which are the following two positions:
(1) According to the following Ayah:
"..Allah only desires to keep away the uncleanness from you, O Ahl al-Bayt! and to purify you a (thorough) purifying (33:33)."
They have an infallible and purified position; and by virtue of this position, no sin ever touches them.
(2) According to valuable holy "Hadith al-Thaqalayn" of the Prophet (S), also mentioned earlier, the Ahl al-Bayt (as) of the Holy Prophet (S) are inseparable from the Holy Qur'an. There will never be a separation between themselves and the Holy Qur'an. As a result, they commit no error and mistake in perceiving the meaning of the Holy Qur'an.
The prerequisite for possessing these two positions is that the words and deeds of the Ahl al-Bayt of the Holy Prophet (S) are the criteria and bases (for following) like those of the Holy Prophet (S) himself. Therefore, the beliefs of Shi'ahs are based on these facts.
Quoting the Holy Prophet (S) Sunni and Shi'ah 'ulama' have related many ahadith on the virtues of 'Ali (as) and all the other Ahl al-Bayt. Three of these virtues will be dealt with here.
(1) In the 6th year after Hijrah, the Christians of the city of Najran selected a group of their dignitaries and scholars and sent them to Madinah. The delegation primarily debated and argued with the Holy Prophet (S), but they were condemned and defeated and Allah revealed the following Ayah of "Al-Mubahalah (cursing)".
"But whoever disputes with you in this matter after what has come to you of knowledge, then say: 'Come let us call our sons and your sons and our women and your women and our near people and your near people, then let us be earnest in prayer, and pray for the curse of Allah on the liars' (3:61)."
According to the order and instruction given through this Ayah, the Holy Prophet (S) proposed that the Christian delegation from Najran participate in requesting the curse of Allah on liars, that is, they had to gather along with their wives and children to pray for the curse of Allah on the liars, so that the Almighty Allah would send upon them His torment.
The Christian delegation from Najran accepted the proposal for Al-Mubahalah and allocated the day after for this purpose. The next day, a great number of Muslims and also the delegation from Najran waited for the Holy Prophet's (S) appearance to see in what form and with what formalities he would arrive and whom he would bring along for Al-Mubahalah.
They saw the Holy Prophet (S) coming out in such a way that he was carrying al-Husayn (as) in his arms and holding al-Hasan's (as) hand in his hand. Behind the Holy Prophet (S) was his daughter, Fatimah (as), and behind her was 'Ali (as). The Holy Prophet (S) ordered these honourable persons accompanying him to say Amin (may it be so) when he prayed.
The delegation of Najran was struck with horror when they saw this holy delegation who entirely displayed truth and reality and who sought no refuge except the protection of the Almighty Allah. The chief of Najran delegation told his colleagues; "By Allah, I see these faces who will annihilate all the Christians of the world if they turn towards Allah."
This was the reason why they came to Muhammad (S) and asked him to excuse them from participating in Al-Mubahalah. The Holy Prophet (S) asked them to submit to the will of Allah and convert to Islam. They said that they were unable to fight with the Muslims but were ready to pay annual tax to live under the protection of Islam. Thus this episode ended.
The following conclusion could be drawn from this incident:
The accompaniment of 'Ali (as), Fatimah (as), al-Hasan (as), al-Husayn (as) with the Holy Prophet (S) in the course of Al-Mubahalah clarified that, in the holy Ayah "our sons, our women, and our near people" refers to none but the Holy Prophet (S), 'Ali(as), Fatimah (as), al-Hasan (as), and al-Husayn (as). In other words, by stating the word "ourselves", the Holy Prophet (S) meant himself and 'Ali (as), by "our women", he meant Fatimah (as), and by "our sons", he meant al-Hasan (as) and al-Husayn (as).
Thus, it becomes crystal clear that 'Ali (as) is in the same rank as the Holy Prophet (S) himself. It also becomes evident that the Ahl al-Bayt (as) of the Holy Prophet (S) were four persons. This is because the members of the household of anyone are those which are commonly called as "ourselves, our women, and our children". If any other persons were considered as theAhl al-Bayt, the Holy Prophet (S) would have taken them along for Al-Mubahalah.
This is why we must judge about the 'Ismah (infallibility) of these four persons, for the Almighty Allah testifies on the 'Ismah and taharah (purity) of the Ahl al-Bayt (as) of the Holy Prophet (S):
"...Allah only desires to keep away the uncleanliness from you, O Ahl al-Bayt! and to purify you a (thorough) purifying (33:33)."
(2) As related by Sunni and Shi'ah 'ulama', the Holy Prophet (S) has stated:
"The parable of my Ahl al-Bayt is that of Nuh's ark; those who boarded were saved while those who did not board were drowned".
(3) In another successive hadith, related by Sunni and Shi'ah 'ulama', the Holy Prophet (S) has stated:
"I leave two valuable things for you which will never be separated from each other till they meet me at Hawd al-Kawthar. They are the Allah's Book, Quran and the Ahl al-Bayt. You will not go astray after me as long as you remain in touch with them intimately and seek refuge under these two".