Musnad Ahmad 30:3062

Waki' narrated to us, Ali—meaning Ibn al-Mubarak—narrated to us, from Yahya, from Ikrimah, from Abu Hurairah, that the Prophet (peace and blessings of Allah be upon him) saw a man driving a sacrificial camel. He said, "Ride it." The man said, "It is a sacrificial camel." He said, "Ride it." He said: So I saw him riding it, and there was a sandal around its neck.