Sunan At-Tirmidhi

Abu Mas'ud [Al-Ansari] said:""I was beating a slave of mine and I heard someone behind me saying: 'Beware O Abu Mas'ud! Beware O Abu Mas'ud!' So I turned around and saw that it was the Messenger of Allah. He said: 'Allah has more power over you than you do over him."" Abu Mas'ud said: ""I have not beaten any slave of mine since then