prayers, and a ritually pure worshipper does not pray behind one who suffers from chronic urinary incontinence; nor do women in a state of purity pray behind a woman experiencing prolonged bleeding; nor does a competent reciter pray behind one who is illiterate; nor does a clothed person pray behind one who is naked.
It is permissible for someone who has performed tayammum (dry ablution) to lead those who have performed wudu (regular ablution), and for a person who has merely wiped over his leather socks to lead those who have washed their feet. A man who is standing may pray behind an imam who is seated, but the one who actually bows and prostrates may not follow an imam who only gestures. One who is praying an obligatory prayer may not pray behind someone engaged in a voluntary prayer, nor may someone observing one obligatory prayer follow an imam observing a different obligatory prayer, whereas a worshipper offering a voluntary prayer may follow an imam praying an obligation.
Whoever follows an imam and then learns that the imam was without wudu must repeat the prayer.
It is disliked for the worshipper to fidget with his garment or his body, to turn over the gravel—except when he cannot prostrate, in which case he may smooth it once—to crack his knuckles, place his hands on his hips, let his garment hang loosely, tie up his hair, or fold up his clothing.
He should not turn his head, squat like a dog, return a salām with either tongue or hand, sit cross-legged unless excused, nor should he eat or drink.
If his ablution is broken during the prayer he should withdraw; if he was the imam, he appoints a deputy, performs wudu, and resumes the prayer, though beginning afresh is better.
If he falls asleep and has a seminal emission, becomes insane, faints, or laughs out loud, he must renew both his ablution and his prayer.
If he speaks in his prayer deliberately or forgetfully, the prayer is invalid.
If his ablution breaks after he has recited the tashahhud, he performs wudu and then gives salām; but if, after that point, he deliberately breaks wudu, speaks, or does anything else that nullifies prayer, his prayer is still deemed complete.
If a person praying with tayammum sees water during the prayer, his prayer is invalid.
If he sees it only after sitting for the length of time needed to recite tashahhud; or if someone wiping over leather socks exceeds the permitted period, or removes the socks with another’s help; or an illiterate worshipper learns a surah; or a naked worshipper finds clothing; or one who was gesturing becomes able to bow and prostrate; or he remembers that he owes a prior prayer; or the time of ʿAṣr enters while he is in the Friday prayer; or a splint that had been wiped over falls away after healing; or a person with a chronic excuse finds that the excuse has ceased—then, in the opinion of Abū Ḥanīfa, his prayer is invalid, whereas Abū Yūsuf and Muḥammad hold that his prayer stands complete.