Sahih Adab al-Mufrad

It is narrated from Sayyiduna Abu Mas’ud (may Allah be pleased with him) who says: I was beating my slave when I heard a voice from behind me, “O Abu Mas’ud! Know that Allah has more power over you than you have over him.” When I turned around, it was the Messenger of Allah (peace and blessings be upon him). I said, “O Messenger of Allah, I have freed him for the sake of Allah.” The Prophet (peace and blessings be upon him) said, “Beware! If you had not done so, the Fire would have engulfed you or the Fire would have touched you.”