Abu Dharr · a Light

He insulted a man's mother and had to be corrected

Abu Dharr al-Ghifari abused a servant by referring to his mother's colour. When the Prophet ﷺ heard of it he said that Abu Dharr was a man in whom something of the age before Islam still remained, and told him: they are your brothers, Allah has placed them under your hand, so feed them from what you eat, clothe them from what you wear, and do not burden them with more than they can bear, and if you do, then help them. The correction was kept because of what came next. Al-Ma'rur ibn Suwayd met Abu Dharr years later, found him and his servant wearing the same cloth, and asked why. That is how the report reached us.

Al-Ma'rur ibn Suwayd, of Abu Dharr · Rabadha

Source · Bukhari 30