Musnad Ahmad 32:1779

Hashim ibn al-Qasim narrated to us, Shu'bah narrated to us, from Hisham ibn Zayd ibn Anas, from Anas, who said: "I entered upon the Prophet, peace and blessings of Allah be upon him, in the *mirbad* (a place where dates are dried), and he was branding sheep." Shu'bah said: "I think he said: 'in their ears.'"