Sunan an Nasai
930
Sahih+2

It was narrated from Abu Hurairah that:The Messenger of Allah (ﷺ) said: "If any one of you says: 'Amin' and the angels in Heaven say Amin, and the one coincides with the other, his previous sins will be forgiven

SahihAbu Ghuddah
SahihAl-Albani