It is narrated from Hazrat Abu Mas'ud (may Allah be pleased with him) that one day I was beating one of my slaves when a voice from behind said, "Leave him!" O Abu Mas'ud! Remember! I turned around and saw that it was the Noble Prophet (peace and blessings be upon him). The Prophet (peace and blessings be upon him) said, "By Allah! You have as much power over this slave as Allah has more power over you." At that very moment, I swore that I would never beat any slave again.