From Sahih Bukhari (Hadith 3228):
Narrated Abu Huraira:Allah's Messenger (ﷺ) said, "When the Imam, during the prayer, says, "Allah hears him who praises Him', say: 'O Allah! Our Lord! All the praises are for You/, for if the saying of anyone of you coincides with the saying of the angels, his past sins will be forgiven
Reference: Bukhari 3228