Sahih Muslim 1661 a
The Book of Oaths
Feeding a slave what one eats and clothing him as one clothes oneself, and not burdening him with more than he bear
Al-Ma'rur b. Suwaid said: We went to Abu Dharr (Ghifari) in Rabadha and he had a mantle over him, and his slave had one like it. We said: Abu Dharr, had you joined them together, it would have been a complete garment. Thereupon he said: There was an altercation between me and one of the persons among my brothers. His mother was a non-Arab. I reproached him for his mother. He complained against me to Allah's Messenger (ﷺ). As I met Allah's Messenger (ﷺ) he said: Abu Dharr, you are a person who still has (in him the remnants) of the days (of Ignorance). Thereupon I said: Allah's Messenger (ﷺ) , he who abuses (other) persons, they abuse (in return) his father and mother. He (the Prophet) said: Abu Dharr, you are a person who still has (the remnants) of Ignorance in him They (your servants and slaves) are your brothers. Allah has put them in your care, so feed them with what you eat, clothe them with what you wear. and do not burden them beyond their capacities; but if you burden them (with an unbearable burden), then help them (by sharing their extra burden).