Sahih al-bukhari:6050 Chapter: Al-Birr and As-Sila Book 78, Hadith 80

Narrated Ma’rur: I saw Abu Dhar wearing a Burd (garment) and his slave too was wearing a Burd, so I said (to Abu
Dhar), “If you take this (Burda of your slave) and wear it (along with yours), you will have a nice suit
(costume) and you may give him another garment.” Abu Dhar said, “There was a quarrel between me
and another man whose mother was a non-Arab and I called her bad names. The man mentioned
(complained about) me to the Prophet. The Prophet (ﷺ) said, “Did you abuse so-and-so?” I said, “Yes” He
said, “Did you call his mother bad names?” I said, “Yes”. He said, “You still have the traits of (the
Pre-lslamic period of) ignorance.” I said. “(Do I still have ignorance) even now in my old age?” He
said, “Yes, they (slaves or servants) are your brothers, and Allah has put them under your command.
So the one under whose hand Allah has put his brother, should feed him of what he eats, and give him
dresses of what he wears, and should not ask him to do a thing beyond his capacity. And if at all he
asks him to do a hard task, he should help him therein.”