Musnad Ahmad 32:782

Hajjaj narrated to us, he said: Shu'bah, he informed us from Hisham ibn Zayd ibn Anas, from his grandfather Anas ibn Malik, who said: "I entered upon the Messenger of Allah, may Allah bless him and grant him peace, while he was branding sheep." Hisham said: "I think he said: 'in their ears.'" He said: "Then he said: 'in their ears,' and he did not doubt."