Hilal bin Yasaf هلال بن يساف · The Book of Oaths

You could find no other part (to slap) but the prominent part of her face. See I was one of the seven sons of Muqarrin, and we had but only one slave-girl. The youngest of us slapped her, and Allah's Messenger (ﷺ) commanded us to set her free. 2097

We used to sell cloth in the house of Suwaid b. Muqarrin, the brother of Nu'man b. Muqarrin. There came out a slave-girl, and she said something to a person amongst us, and he slapped her. Suwaid was enraged-the rest of the hadlth is the same.