Musannaf Ibn Abi Shayba 19:460

Abu Bakr narrated to us, he said: Waki’ narrated to us, from Musa ibn ‘Ubaydah, from Bakr ibn Dawud, that ‘Ali established the prescribed punishment (hadd) upon a man who had intercourse with a slave girl from the khums (the one-fifth share of the spoils of war).