Musnad Abu Ya'la al-Mawsili 112:8

Suwayd ibn Sa'id narrated to us, Ali ibn Mushir narrated to us, from Isma'il, from al-Hasan, from Anas ibn Malik, who said: The Messenger of Allah (may Allah bless him and grant him peace) came upon a man driving a sacrificial camel while he was barefoot. He said, "Ride it." The man said, "O Messenger of Allah, it is a sacrificial camel." He said, "Ride it." So he rode it.