(30) بَاب جَوَازِ وَسْمِ الْحَيَوَانِ غَيْرِ الْآدَمِيِّ فِي غَيْرِ الْوَجْهِ وَنَدْبِهِ فِي نَعَمْ الزَّكَاةِ وَالْجِزْيَةِ
Anas reported that when his mother gave birth to a child they brought that child to Allah's Messenger (ﷺ) so that he might chew some dates and touch his palate with them. and Allah's Apostle (ﷺ) was at that time in the fold busy in cauterising the animals Shu'ba said:
So far as I know (he was cauterising) their ears.
Reference: Sahih Muslim 2119 b
In-book reference: Book 37, Hadith 166
USC-MSA web (English) reference(deprecated numbering scheme): Book 24, Hadith 5286