Abu Huraira reported:
The Messenger of Allah ( صلی اللہ علیہ وسلم ) said: The Imam is appointed, so that he should be followed, so don't be at variance with him. Recite takbir when he recites it; bow down when he bows down and when he says: Allah listens to him who praises Him, say: O Allah, our Lord, to Thee be the Praise. And when he (the Imam) prostrates, you should also prostrate, and when he says prayer sitting, you should all observe prayer sitting.