Sunan An-Nasa'i

It was narrated that Abu Hurairah said:""The Messenger of Allah (ﷺ) said: 'The Imam is appointed to be followed, so when he says the takbir, say the takbir, and when he recites, be silent, and when he says: ""Sami' Allahu liman hamidah (Allah hears those who praise Him),"" say: ""Allahumma rabbana lakal-hamd (Our Lord, to You be praise)