Musnad Abu Ya'la al-Mawsili 129:152

Zuhayr narrated to us, Yazid bin Harun narrated to us, Humayd al-Tawil informed us, from Anas bin Malik: That the Messenger of Allah (may Allah bless him and grant him peace) passed by a man driving a sacrificial camel. He said, "Ride it." The man said, "It is a sacrificial camel." He said, "Ride it."