´It was narrated from Abu Hurairah that:` The Messenger of Allah (ﷺ) said: "When the Imam says Amin, say Amin, for if a person's Amin coincides with the Amin of the angels, his previous sins will be forgiven.'"
Hadith ReferenceSunan an-Nasa'i / The Book of the Commencement of the Prayer / Hadith: 929
Hadith Gradingالألبانی:صحيح | زبیر علی زئی:متفق عليه