Chapter 28: The Book of Oaths
Abu Mas' ud al-Badri reported: I was beating my slave with a whip when I heard a voice behind me: Understand, Abu Masud; but I did not recognise the voice due to intense anger. He (Abu Mas' ud) reported: As he came near me (I found) that he was the Messenger of Allah (ﷺ) and he was saying: Bear in mind, Abu Mas' ud; bear in mind. Abu Mas' ud. He (Aba Maslad) said: threw the whip from my hand. Thereupon he (the Holy Prophet) said: Bear in mind, Abu Mas' ud; verily Allah has more dominance upon you than you have upon your slave. I (then) said: I would never beat my servant in future.
Sahih Muslim 1659a