The prayer led by a sinful person is invalid, whether for an upright person or for another sinful person. A woman may not lead men in prayer, and neither may an intersex person. If a mute person leads, or if a person with a speech impediment that causes him to substitute one letter for another leads, the prayer of those who follow him is invalid, unless they have the same muteness or speech impediment.

The minimum required of such an imam, in terms of recitation and jurisprudence, is that he have memorized Umm al-Qur’an (the Mother of the Quran), meaning al-Fatihah, and know the rulings of prayer, since this is the minimum that the prayer requires. It is preferable, however, that he have memorized the entire Quran and know all the relevant rulings.

If a jurist who is not a reciter and a reciter who is not a jurist are both present, the reciter takes precedence over the jurist, provided that he knows the rulings of prayer. This is because recitation—and reciting more of the Quran—is certain to be needed, whereas whatever unexpected situations may arise for him during the prayer is not certain to occur, while we have already taken knowledge of its rulings into consideration.