Musannaf Ibn Abi Shayba 13:1225

Abu Bakr narrated to us, he said: Waki’ narrated to us, he said: Hasan ibn Salih narrated to us, from Mutarrif, from a man who is called Hajjaj, from Shurayh, regarding a man who usurped a slave and then utilized his labor (or profited from him): He said, "He must return the profit."