Suwaid bin Ghafala · The Book of Oaths

Don't you know that it is forbidden (to strike the) face. He said: You see I was the seventh one amongst my brothers during the lifetime of Allah's Messenger (ﷺ), and we had but only one servant. One of us got enraged and slapped him. Thereupon Allah's Messenger (ﷺ) commanded us to set him free.