How must the followers alert the Imam when he makes a mistake in prayer (suhū)?
Chapter on the Two Prostrations of Forgetfulness
Al-Mughni
Book of Prayer
Primary text
When the Imam errs and performs an action out of its proper place, the followers must alert him. Men must alert him by saying 'Subhan Allah' (Glory be to Allah). Women must alert him by clapping their palms against the backs of their other hands. This is the position of Al-Shafi'i. Evidence for this distinction is found in the Hadith reported by Abu Hurayrah stating: "Tasbih (glorification) is for men, and clapping is for women." Another Hadith transmitted by Sahl ibn Sa'd confirms this, stating: "If something happens to you in your prayer, men should say Subhan Allah, and women should clap." Furthermore, the Prophet (peace be upon him) himself used to signal responses to greetings during prayer by pointing with his hand, as narrated by Ibn 'Umar and Suhayb.
Supporting text
Malik holds that both men and women should use 'Subhan Allah' for notification, based on the Prophet's command: 'Whoever has something occur during his prayer, let him say: Subhan Allah,' which is agreed upon (Muttafaqun 'alayh). A view attributed to Abu Hanifa suggests that alerting a person through tasbih, Quran recitation, or signaling invalidates the prayer because it constitutes human discourse. This is supported by a narration from Abu Ghatafan via Abu Hurayrah stating that the Prophet (peace be upon him) said: 'Whoever signals with his hand in prayer for comprehension or understanding has broken the prayer.' However, the narration supporting Abu Hanifa's view is considered weak because Abu Ghatafan is unknown.