Sahih Muslim | Book 15 | Hadith Number 4084

Narrated by Suwaid b. Muqarrin
Suwaid b. Muqarrin reported that he had a slave-girl and a person (one of the members of the family) slapped her, whereupon Suwaid said to him: 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 (may peace be upon him), and we had but only one servant. One of us got enraged and slapped him. Thereupon Allah's Messenger (may peace be upon him) commanded us to set him free.