Musnad Abu Ya'la al-Mawsili 129:93

Muhammad ibn al-Minhal al-Darir narrated to us, Yazid ibn Zuray' narrated to us, Humayd narrated to us, from Anas: He said: While a man was driving a sacrificial camel, the Messenger of Allah (peace and blessings of Allah be upon him) said to him, "Ride it." He said, "It is a sacrificial camel, O Messenger of Allah." He said, "Ride it, even if it is a sacrificial camel."