Musnad Ahmad 30:2360

Abu Mu'awiyah and Ibn Numayr narrated to us, they said: Muhammad ibn 'Amr narrated to us, from Abu al-Hakam, the freed slave of the Laythis, from Abu Hurayrah, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "There is no betting except in a hoof or a foot."