Mukhtasar Muslim

Sayyiduna Abu Mas'ud Ansari (may Allah be pleased with him) says: I was beating my slave when suddenly I heard a voice from behind, saying, "Abu Mas'ud! Know that indeed Allah has more power over you than you have over this slave." I turned around and saw that it was the Messenger of Allah (peace and blessings be upon him). I said, "O Messenger of Allah! I have set him free for the sake of Allah (i.e., without any price or condition)." The Prophet (peace and blessings be upon him) said, "If you had not done so, the fire of Hell would have burned you or touched you."