Imam Abu Bakr, may Allah have mercy on him, says that the evidence for this issue is the hadith of the Prophet Muhammad (peace be upon him) that the person who has memorized more of the Qur'an should lead the people in prayer (whether he is a son or a freed slave).

And the evidence that the prayer of the imam may be deficient while the prayer of the follower is complete, contrary to the statement of those who claim that the prayer of the follower is connected to the prayer of the imam—if the prayer of the imam is invalid, then the prayer of the follower is also invalid—is the claim of...

Sayyiduna Uqbah bin Amir (may Allah be pleased with him) narrates that I heard the Messenger of Allah (peace and blessings be upon him) say: "Whoever leads the people in prayer at the correct (initial) time and performs the prayer completely, then both he and the followers will receive reward. And whoever falls short or is negligent in it, then its sin will be upon the imam alone, not upon the followers." This is the narration of Ibn Wahb. The meaning of the hadith from all the narrators is the same.