Language:
كتاب بدء الخلق
59  
Beginning of Creation
(7)
Chapter: If anyone says Amin [during the Salat (prayer) at the end of the recitation of Surat Al-Fatiha]
(7)
بَابُ إِذَا قَالَ أَحَدُكُمْ آمِينَ. وَالْمَلاَئِكَةُ فِي السَّمَاءِ، فَوَافَقَتْ إِحْدَاهُمَا الأُخْرَى، غُفِرَ لَهُ مَا تَقَدَّمَ مِنْ ذَنْبِهِ
Sahih al-Bukhari 3235

Narrated Masruq:

I asked Aisha "What about His Statement:-- "Then he (Gabriel) approached And came closer, And was at a distance Of but two bow-lengths Or (even) nearer?" (53.8-9) She replied, "It was Gabriel who used to come to the Prophet (ﷺ) in the figure of a man, but on that occasion, he came in his actual and real figure and (he was so huge) that he covered the whole horizon."

حَدَّثَنِي مُحَمَّدُ بْنُ يُوسُفَ، حَدَّثَنَا أَبُو أُسَامَةَ، حَدَّثَنَا زَكَرِيَّاءُ بْنُ أَبِي زَائِدَةَ، عَنِ ابْنِ الأَشْوَعِ، عَنِ الشَّعْبِيِّ، عَنْ مَسْرُوقٍ، قَالَ قُلْتُ لِعَائِشَةَ ـ رضى الله عنها ـ فَأَيْنَ قَوْلُهُ ‏{‏ثُمَّ دَنَا فَتَدَلَّى * فَكَانَ قَابَ قَوْسَيْنِ أَوْ أَدْنَى‏}‏ قَالَتْ ذَاكَ جِبْرِيلُ كَانَ يَأْتِيهِ فِي صُورَةِ الرَّجُلِ، وَإِنَّهُ أَتَاهُ هَذِهِ الْمَرَّةَ فِي صُورَتِهِ الَّتِي هِيَ صُورَتُهُ، فَسَدَّ الأُفُقَ‏.‏
Reference : Sahih al-Bukhari 3235
In-book reference : Book 59, Hadith 46
USC-MSA web (English) reference : Vol. 4, Book 54, Hadith 458
  (deprecated numbering scheme)