What is the ruling when the Imam breaks his ritual purity (hadath) during congregational prayer?
Chapter on Praying with Impurity and Other Matters
Al-Mughni
Book of Prayer
Primary text
If the Imam experiences ritual impurity (hadath), he must appoint a successor (yastakhlif) to complete the prayer for the congregation. This ruling is supported by Umar, Ali, 'Alqamah, 'Ata', al-Hasan, al-Nakha'i, al-Thawri, al-Awza'i, al-Shafi'i, and the Ashab al-Ra'y (Hanafi school). The primary evidence is the action of Umar ibn al-Khattab, who, after being wounded, took the hand of Abd al-Rahman ibn 'Awf and put him forward to complete the prayer, which occurred in the presence of the Companions without objection, indicating consensus (ijma'). If the Imam does not appoint a successor and a member of the congregation steps forward to lead the rest, the prayer is valid. It is also valid for them to pray individually (whadan).
Supporting text
A narration attributed to Ahmad holds that the prayer of the followers (ma'mumun) is invalidated because the condition for the Imam's prayer validity was lost, similar to if the Imam intentionally broke purity. Abu Bakr also held this view as a single narration. Another view, attributed to the later opinion of al-Shafi'i, prefers that the followers pray individually if this occurs.