And the Prophet (peace and blessings be upon him) said: The Imam is appointed only so that he may be followed, so do not differ from the Imam. When he says the takbeer, you also say the takbeer. When he bows (in ruku'), you also bow. When he says "Sami' Allahu liman hamidah," you say "Allahumma Rabbana lakal hamd." When he prostrates, you also prostrate. And when he prays sitting, then all of you should also pray sitting.