Saying "Sami'a Allahu liman Hamidah," Rabbana wa lakal-hamd," and "Amin" — Sahih Muslim 409 a

The Messenger of Allah (ﷺ) said: When the Imam says:" Allah listens to him who praises Him." you should say:" O Allah, our Lord for Thee is the praise." for if what anyone says synchronises with what the angels say, his past sins will be forgiven.