If anyone says Amin [during the Salat (prayer) at the end of the recitation of Surat Al-Fatiha] Sahih al-Bukhari 3232
Arabic hadith text
حَدَّثَنَا قُتَيْبَةُ، حَدَّثَنَا أَبُو عَوَانَةَ، حَدَّثَنَا أَبُو إِسْحَاقَ الشَّيْبَانِيُّ، قَالَ سَأَلْتُ زِرَّ بْنَ حُبَيْشٍ عَنْ قَوْلِ اللَّهِ، تَعَالَى {فَكَانَ قَابَ قَوْسَيْنِ أَوْ أَدْنَى * فَأَوْحَى إِلَى عَبْدِهِ مَا أَوْحَى}. قَالَ حَدَّثَنَا ابْنُ مَسْعُودٍ أَنَّهُ رَأَىجِبْرِيلَ لَهُ سِتُّمِائَةِ جَنَاحٍ.
Translation
Narrated Abu 'Is-haq-Ash-Shaibani
I asked Zir bin Hubaish regarding the Statement of Allah: "And was at a distance Of but two bowlengths Or (even) nearer; So did (Allah) convey The Inspiration to His slave (Gabriel) and then he (Gabriel) Conveyed (that to Muhammad). (53.9-10) On that, Zir said, "Ibn Mas`ud informed us that the Prophet (ﷺ) had seen Gabriel having 600 wings."