“The Messenger of Allah (ﷺ)
said: ‘The Imam has been appointed to be followed, so when he says
Allahu Akbar, then say Allahu Akbar, when he recites, then listen
attentively; when he says: Not (the way) of those who earned Your
anger, nor of those who went astray, then say Amin; when he bows
then bow; when he says Sami’ Allahu liman hamidah (Allah hears
those
who praise Him), then say Allahumma Rabbana wa lakal-hamd (O
Allah,
our Lord, to You is the praise);” when he prostrates then
prostrate;
and if he prays sitting down then all of you pray sitting
down.’”
Sunan Ibn Majah Book 5, Hadith 44