Musnad Ahmad 937:87

Qutaybah ibn Sa'id narrated to us, Layth ibn Sa'd narrated to us, from 'Ubayd Allah ibn Abi Ja'far, from al-Himsi, from Abu Talib, from Abu Dharr, who said: I heard the Messenger of Allah, peace and blessings of Allah be upon him, say: "Whoever commits adultery with a slave woman whom he does not own, she commits adultery, Allah will lash him on the Day of Resurrection with a whip of fire."