I came to the Messenger of Allah ﷺ while he was branding sheep. Hisham said, "I think he said, 'on their ears.'" Then he later said, "on their ears," without any doubt.
حدثنا حجاج قال شعبة أنبأناه عن هشام بن زيد بن أنس
دخلت على رسول الله ﷺ وهو يسم غنما قال هشام أحسبه قال في آذانها قال ثم قال بعد في آذانها ولم يشك
Its isnad is sahih, and Hisham bin Zayd, the grandson of Anas, is trustworthy. Bukhari narrated it, 3/362, no. 1502, Fath, in the Book of zakat, chapter on branding the camels of charity, as did Muslim, 4/1909, no. 2144, in the Book of the Virtues of the Companions, chapter on the virtues of Abu Talha.