If anyone says Amin [during the Salat (prayer) at the end of the recitation of Surat Al-Fatiha] Sahih al-Bukhari 3229
Arabic hadith text
حَدَّثَنَا إِبْرَاهِيمُ بْنُ الْمُنْذِرِ، حَدَّثَنَا مُحَمَّدُ بْنُ فُلَيْحٍ، حَدَّثَنَا أَبِي، عَنْ هِلاَلِ بْنِ عَلِيٍّ، عَنْ عَبْدِ الرَّحْمَنِ بْنِ أَبِي عَمْرَةَ، عَنْ أَبِي هُرَيْرَةَ ـ رضى الله عنه ـ عَنِ النَّبِيِّ صلى الله عليه وسلم قَالَ "إِنَّ أَحَدَكُمْ فِي صَلاَةٍ مَا دَامَتِ الصَّلاَةُ تَحْبِسُهُ، وَالْمَلاَئِكَةُ تَقُولُ اللَّهُمَّ اغْفِرْ لَهُ وَارْحَمْهُ. مَا لَمْ يَقُمْ مِنْ صَلاَتِهِ أَوْ يُحْدِثْ "
Translation
Narrated Abu Huraira
The Prophet (ﷺ) said, "As long as any-one of you is waiting for the prayer, he is considered to be praying actually, and the angels say, 'O Allah! Be merciful to him and forgive him', (and go on saying so) unless he leaves his place of praying or passes wind (i.e. breaks his ablution).