And it is reported from Muhammad ibn 'Amr ibn al-Mustaliqi al-Khuza'i that Uthman led the people in the dawn prayer, and when it became morning and the day rose, he found traces of janaba (major ritual impurity). He said: "How grave it is, by Allah, how grave it is, by Allah!" So he repeated the prayer, but did not order them to repeat it. It is also reported from Ali that he said: "If a person in a state of major ritual impurity leads the people in prayer and completes the prayer with them, I order him to perform ghusl (ritual bath) and repeat, but I do not order them to repeat." It is also reported from Ibn Umar that he led them in the morning prayer, then remembered that he had prayed without wudu', so he repeated it, but they did not repeat. Al-Athram reported all of this. This is a matter of common knowledge, and no opposition to it has been reported, so it constitutes a consensus (ijma'). What was reported from Ali in opposition to this has not been authenticated. Furthermore, it is reported from al-Bara' ibn 'Azib that the Prophet (peace be upon him) said: "If a person in a state of major ritual impurity leads the people in prayer, he shall repeat his prayer, but the people's prayer is complete." This was extracted by Abu Sulayman Muhammad ibn al-Husayn al-Harrani in a "juz'" (monograph). This is because ritual impurity (hadath) is something hidden, and there is no way for those being led (ma'mum) to know of it from the Imam, so they are excused for following him. This differs from the case where the Imam knows of his own impurity, for he would then be mocking the prayer and doing what is not permissible. Likewise, if the follower knows, he has no excuse for following him. Analogizing the excused person to the one who is not is invalid. The ruling on impurity is the same as the ruling on ritual impurity, because it is one of the two purities, so it resembles the other. It is also similar in its meaning regarding its hidden nature from both the Imam and the follower; in fact, the ruling on impurity is lighter and its hidden nature is more prevalent. However, there is another narration regarding impurity, which is that the prayer of the Imam is also valid if he forgot it.

Section: If he knows of his own ritual impurity during the prayer, or the followers know of it, they are required to restart the prayer. Ahmad explicitly stated this. Al-Athram said: I asked Abu 'Abd Allah about a man who led people in prayer while he was not in a state of purity, and he remembered during part of the prayer? He said: "It pleases me that they restart the prayer." I said to him: "Should he say to them, 'Restart the prayer'?" He said: "No, rather he should turn away and speak, and they should restart the prayer themselves." Ibn 'Aqil said: There is another narration from Ahmad, may Allah have mercy on him, that if the followers know [of it], they may continue their prayer. Al-Shafi'i said: They may continue their prayer, whether he knew of it or the followers knew of it; because what has passed of their prayer is valid, so they may build upon it, just as if he stood up for a fifth rak'ah and they prompted him but he did not return. Our view is that he followed someone whose prayer is invalid, with knowledge by both or one of them, which resembles the case of following a woman [as an Imam]. This is only excused when ignorance persists for both of them due to consensus, and because it is difficult for the followers to repeat the prayer when ignorance persists due to their dispersion, unlike when they know [of it] during the prayer. If some of the followers know while others do not, the explicit text indicates that the prayer of all is invalidated, though it is more appropriate that the invalidation be limited to those who knew, and not those who were ignorant; because it is a nullifying factor specific to him, so the invalidation is specific to him, just like his own ritual impurity.