Musnad Ahmad 30:1319

Hisham ibn Sa'id narrated to us, Abu 'Awanah narrated to us, from 'Umar ibn Abi Salamah, from his father, from Abu Hurayrah, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "If the slave of one of you steals, then let him sell him, even if for a nish."