Narrated Anas:

I brought a brother of mine to the Prophet to do Tahnik for him while the Prophet 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.)

حَدَّثَنَا أَبُو الْوَلِيدِ، حَدَّثَنَا شُعْبَةُ، عَنْ هِشَامِ بْنِ زَيْدٍ، عَنْ أَنَسٍ، قَالَ دَخَلْتُ عَلَى النَّبِيِّ ﷺ بِأَخٍ لِي يُحَنِّكُهُ، وَهْوَ فِي مِرْبَدٍ لَهُ، فَرَأَيْتُهُ يَسِمُ شَاةً ـ حَسِبْتُهُ قَالَ ـ فِي آذَانِهَا.