"What is meant by ""The Imam is appointed to be followed..."", and is it obligatory to follow the Imam if he deliberately adds a pillar (of prayer)? "

"In the two Sahihs (collections of authentic hadith), the Prophet (peace and blessings of Allah be upon him) said: ""The Imam is appointed to be followed; so when he says 'Allahu Akbar,' say 'Allahu Akbar'; when he bows, bow; when he raises his head, raise your heads; when he says, 'Samia Allahu liman hamidah' (Allah hears those who praise Him), say 'Rabbana wa laka al-hamd' (Our Lord, and to You be praise); and when he prostrates, prostrate."" This indicates the obligation of the follower (ma'mum) to follow the Imam in saying 'Allahu Akbar,' standing, sitting, bowing, and prostrating, and he performs these actions after the Imam. The meaning of ""The Imam is appointed to be followed"" according to Al-Shafi'i, is in outward actions. Otherwise, it is permissible to pray an obligatory prayer behind a voluntary prayer, and vice versa, and to pray Dhuhr behind Asr. Malik and Abu Hanifa differed with him on this. And if the Imam adds a rak'ah (unit of prayer) or a pillar (rukn), it is not permissible to follow him in that, and the prayer of the follower is invalidated if he follows him knowingly and intentionally.

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