“I have left among you the book of Allah and my Ahlulbayt.”
Shias like to argue that Ahlulbayt are limited to the fourteen infallibles. Even though there are no evidences that the term should be limited to them, we find them insisting that fallible members of the household should be excluded.
We are all aware that the Prophet – peace be upon him – spoke to Muslims in a language that they could understand, so unless he specifically limited the term to refer to fourteen people, there is no justification for this understanding.
To confirm this, we decided to seek Ali’s understanding of the term and his usage of it in Nahjul Balagha.
In Letter #9 (248), we find Ali saying that when the crisis reddened in battle, the Prophet – peace be upon him – would use Ahlulbayt to defend his companions. He then lists their names, and they include Ubaida bin Al-Harith, Hamza bin Abdul Muttalib, and Ja’far bin Abi Talib.
Thus, we come to the conclusion that Ali used the term Ahlulbayt to refer to those that were related to the Prophet – peace be upon him – even though they were never seen as infallibles. It is also very important to keep in mind that Ubaida bin Al-Harith is not from Bani Hashim, but rather, he is from Bani Al-Muttalib, the brother of Hashim.
Truly, it is very important to understand the roots and usages of these definitions before adopting ideologies that go against the very definitions that was used by Ali bin Abi Talib.