When you look at the Muslims of the Prophet's days...
When you look at the Muslims of the Prophet's days, you can find no one who might be more knowledgeable, informed, reliable and closer to the Prophet than the Ahlu'l-bayt, the family of the Prophet.
After all, it is the Qur'an which testifies to their spiritual purity of highest category by saying, "Verily Allah intends to purify you, O the Ahlu'l-bayt, a thorough purification." (33:33) Combine this verse about Ahlu'l-bayt's purity with the following: "It is the holy Qur'an in a preserved tablet, none shall touch it but the purified ones." (56:79) This shows that the Ahlu'l-bayt could understand the Qur'an better than any other follower of (peace be upon him).
Allay says, " Say (O Muhammad), 'I do not ask from you any reward (for bringing the message to you) except to love my near ones.' " (42:23) See that it is Allah who is commanding His messenger to ask the people to love his family. If they were not truthful, reliable, and worthy of following, would Allah command us to love them? These few verses are enough to show that the best commentators of the Qur'an and the most authentic source for the Prophet's sunnah are the Imams of Ahlu'l-bayt.
The Prophet himself said, "I am leaving among you two worthy things. As long as you hold on to them both, you will never be led astray after me. One of these two is greater than the other: the Book of Allah (which is a rope hanging from the heaven to the earth) and my descendants, my Ahlu'l-bayt. These two things will not separate from each other until they come to me at the (fountain of) Kauthar (in the hereafter).
Therefore, see how you recompense me by the way you deal with them." This is not the place to discuss about the authenticity of the above hadith, but it will suffice to quote Ibn Hajar al-Makki, a famous anti-Shi'ah polemicist.
After recording this hadith from various companions who had heard it from the Prophet at various places and times, Ibn Hajar says, " And there is no contradiction in this [numerous reports] since there was nothing to prevent the Prophet from repeating [this statement] at those various places because of the importance of the holy Book and the pure Family."[^1] We can conclude from these verses and the hadith mentioned above that the Ahlu'l-bayt are the most authentic and the best source for the sunnah , and therefore we prefer them to all other sources.