Musannaf Ibn Abi Shayba 13:1097

Abu Bakr narrated to us, he said: Abdullah bin Numayr narrated to us, from al-A’mash, who said: A neighbor of mine, a fuller (qassar) who was called Thabit, ordered me, saying: "Ask Ibrahim about a man who gave a garment to his slave, and it was lost." So I asked him, and he said: "Does he not know that he is a slave?" I said: "Yes." He said: "He is liable (damin)."