Translation
(61) Virtues and Merits of the Prophet (pbuh) and his Companions
كتاب المناقب
(23) Chapter: The description of the Prophet (saws)
(23) باب صِفَةِ النَّبِيِّ صلى الله عليه وسلم
Sahih al-Bukhari 3552 

Narrated Abu 'Is-haq:

Al-Bara' was asked, "Was the face of the Prophet (as bright) as a sword?" He said, "No, but (as bright) as a moon."

حَدَّثَنَا أَبُو نُعَيْمٍ، حَدَّثَنَا زُهَيْرٌ، عَنْ أَبِي إِسْحَاقَ، قَالَ سُئِلَ الْبَرَاءُ أَكَانَ وَجْهُ النَّبِيِّ صلى الله عليه وسلم مِثْلَ السَّيْفِ قَالَ لاَ بَلْ مِثْلَ الْقَمَرِ‏.‏
Reference : Sahih al-Bukhari 3552
In-book reference : Book 61, Hadith 61
USC-MSA web (English) reference : Vol. 4, Book 56, Hadith 752
  (deprecated numbering scheme)