Some disagreement occurred between Abu Dharr and Bilal. As a result, Abu Dharr said to Bilal, “You son of a black woman.”
The Messenger of Allah (sal Allahu alaihi wa sallam) was extremely upset by Abu Dharr’s comment and rebuked him saying, “That is too much, Abu Dharr. He who has a white mother has no advantage which makes him better than the son of a black mother.”
This rebuke had a profound effect on Abu Dharr, who then put his head on the ground, swearing that he would not raise it until Bilal had put his foot on it.
This hadith tells us that there is no place for racism in Islam. It also shows us the lofty character of the Sahabah: When they made a mistake they would repent immediately on realising it and not insist on their sin.