وَقَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ : " إِذَا قَالَ : أَحَدُكُمْ آمِينَ ، وَالْمَلَائِكَةُ فِي السَّمَاءِ ، فَيُوَافِقُ إِحْدَاهُمَا الْأُخْرَى ، غُفِرَ لَهُ مَا تَقَدَّمَ مِنْ ذَنْبِهِ " .
And the Noble Prophet (peace and blessings be upon him) said: When any one of you says Ameen and the angels also say Ameen at the same time, then the one whose Ameen coincides with the Ameen of the angels, all his past sins will be forgiven.