Musnad Ahmad 30:619

'Abd al-Razzaq narrated to us, Ma'mar narrated to us, from Yahya ibn Abi Kathir, from 'Ikrimah, from Abu Hurayrah, who said: The Prophet, peace and blessings of Allah be upon him, passed by a man driving a sacrificial camel. The Prophet, peace and blessings of Allah be upon him, said: "Ride it." The man said: "It is a sacrificial camel." He said: "Ride it." Abu Hurayrah said: I saw him walking alongside the Prophet, peace and blessings of Allah be upon him, and it had a sandal tied around its neck.