From Sahih Muslim (Hadith 5555):
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: Muslim 5555