Sahih al-Bukhari, Book 24, Hadith 103 (In-Book) ⓘ

Narrated Anas bin Malik: I took `Abdullah bin Abu Talha to Allah's Messenger to perform Tahnik for him. (Tahnik was a custom among the Muslims that whenever a child was born they used to take it to the Prophet who would chew a piece of date and put a part of its juice in the child's mouth). I saw the Prophet and he had an instrument for branding in his hands and was branding the camels of Zakat.

حَدَّثَنَا إِبْرَاهِيمُ بْنُ الْمُنْذِرِ، حَدَّثَنَا الْوَلِيدُ، حَدَّثَنَا أَبُو عَمْرٍو الأَوْزَاعِيُّ، حَدَّثَنِي إِسْحَاقُ بْنُ عَبْدِ اللَّهِ بْنِ أَبِي طَلْحَةَ، حَدَّثَنِي أَنَسُ بْنُ مَالِكٍ ـ رضى الله عنه ـ قَالَ غَدَوْتُ إِلَى رَسُولِ اللَّهِ صلى الله عليه وسلم بِعَبْدِ اللَّهِ بْنِ أَبِي طَلْحَةَ لِيُحَنِّكَهُ، فَوَافَيْتُهُ فِي يَدِهِ الْمِيسَمُ يَسِمُ إِبِلَ الصَّدَقَةِ‏.‏