Shu'bah said: Muhammad bin al-Munkadir asked me my name. I told him: "Shu'bah." He said: Abu Shu'bah narrated to us, from Suwayd bin Muqarrin (may Allah be pleased with him), that a man slapped his slave, or some person, and Suwayd said: Do you not know that the face is greatly sacred? In the time of the Messenger I saw seven brothers who had one slave; one of them slapped the slave, and he (peace and blessings be upon him) ordered the seven: "Set him free."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب النفقات / 15804