his condition, whereas the one who conceals it, the one who prays behind him is excused. This has an effect on the validity of the prayer, which is why repetition is not obligatory behind one who is in a state of minor ritual impurity (hadath) or who is in a state of ritual impurity (najis) if their condition is not known, due to the hidden nature of that in them. However, it is obligatory for the one who prays behind a disbeliever or an illiterate person (ummi) because their condition is usually manifest. It has been narrated from Ahmad that one should not pray behind an innovator under any circumstances. He said in the report of Abu al-Harith: "Do not pray behind a Murji'i, a Rafidi, or a fasiq (transgressor), unless you fear them, in which case you pray and then repeat the prayer." Abu Dawud said: Ahmad said: "Whenever you pray behind someone who says the Quran is created, then repeat [the prayer]." I said: "And you know he holds that view?" He said: "Yes." From Malik it is narrated that one should not pray behind the people of innovation. Thus, it follows from this that whoever prays behind an innovator who manifests his innovation must repeat the prayer, and regarding the one who does not manifest it, there are two narrations on whether or not one should repeat the prayer behind him. Al-Hasan, Abu Ja'far, and al-Shafi'i permitted prayer behind people of innovation based on the saying of the Messenger of Allah (peace and blessings of Allah be upon him): "Pray behind whoever says 'There is no god but Allah'." Narrated by al-Daraqutni (3). This is because he is a man whose prayer is valid, so following him in prayer is valid just as it is with anyone else. Nafi' said: Ibn 'Umar used to pray with the Khashabiyya (4) and the Khawarij during the time of Ibn al-Zubayr while they were fighting each other. It was said to him: "Do you pray with these and with those, while some of them kill others?" He said: "Whoever says: 'Hayya 'ala al-salah (Come to prayer)', I respond to him; and whoever says: 'Hayya 'ala al-falah (Come to success)', I respond to him; and whoever says: 'Hayya 'ala qatl akhika al-muslim (Come to killing your Muslim brother) and taking his wealth', I say: 'No'." Narrated by Sa'id. Ibn al-Mundhir and some of the Shafi'is said: "Whoever we declare a disbeliever due to his innovation, such as the one who [lies about Allah or His Messenger] (5) through his innovation, we do not pray behind him, and whoever we do not declare a disbeliever..."