Sahih al-Bukhari 1502
Narrated Anas bin Malik:
I took `Abdullah bin Abu Talha to Allah's Messenger (ﷺ) 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 (ﷺ) who would 
chew a piece of date and put a part of its juice in the child's mouth). I saw the Prophet (ﷺ) 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.‏