سنن أبي داود

Narrated Mu'awiyah ibn Suwayd ibn Muqarrin:

I slapped a freed slave of ours. My father called him and me and said: Take retaliation on him. We, the people of Banu Muqarrin, were seven during the time of the Prophet (ﷺ),and we had only a female servant. A man of us slapped her. The Messenger of Allah (ﷺ) said: Set her free. They said: We have no other servant than her. He said: She must serve them till they become well off. When they become well off, they should set her free.