Sahih al-Bukhari 5542
Sahih al-Bukhari · Book 72: Hunting, Slaughtering · Branding the faces
Narrated Anas:
حَدَّثَنَا أَبُو الْوَلِيدِ ، حَدَّثَنَا شُعْبَةُ ، عَنْ هِشَامِ بْنِ زَيْدٍ ، عَنْ أَنَسٍ ، قَالَ دَخَلْتُ عَلَى النَّبِيِّ صلى الله عليه وسلم بِأَخٍ لِي يُحَنِّكُهُ، وَهْوَ فِي مِرْبَدٍ لَهُ، فَرَأَيْتُهُ يَسِمُ شَاةً ـ حَسِبْتُهُ قَالَ ـ فِي آذَانِهَا.
I brought a brother of mine to the Prophet (ﷺ) to do Tahnik for him while the Prophet (ﷺ) was in a sheep fold of his, and I saw him branding a sheep. (The sub-narrator said: I think Anas said, branding it on the ear.)