What is the ruling on prayers performed by Muslims behind a non-Muslim imam, unknowingly, and what must they do after becoming aware of it? Is it permissible for someone who prayed behind an imam whose prayer they were not confident in due to the imam's errors to repeat the prayer, and will they receive the reward for congregational prayer?

The imamate of a disbeliever is invalid by the unanimous consensus of scholars, and the prayer must be repeated if his disbelief becomes apparent after the prayer. The prayer of one who recites well is not valid if led by an unlettered Imam who cannot recite Al-Fatiha properly, according to the majority of scholars, and the prayer must be repeated unless the worshipper is like him. The prayer must be repeated if the Imam makes a mistake in Al-Fatiha that alters the meaning, such as changing the diacritic of the letter ta in (An'amta) to a damma. Tajweed is not a condition for the validity of the prayer.