The Messenger of Allah (ﷺ) said: SayAmin when the Imam says Amin, for it anyone's utterance of Amin synchronises with that of the angels, he will be forgiven his past sins.
Sahih Muslim Book 4, Hadith 77
← Previous Hadith A hadith like this is narrated by Abu Huraira by another chain of transmitters.

Sahih Muslim Book 4, Hadith 76 Next Hadith → I heard from the Messenger of Allah (ﷺ) the hadith like one transmitted by Malik, but he made no mention of the words of Shihab.

Sahih Muslim Book 4, Hadith 78