Narrated Abu Hurairah:A man brought the Prophet (ﷺ) a black slave girl. He said: Messenger of Allah, emancipation of believing slave is due to me. He asked her: Where is Allah ? She pointed to the heaven with her finger. He then asked her: Who am I ? She pointed to the Prophet (ﷺ) and to the heaven, that is to say: You are the Messenger of Allah. He then said: Set her free, she is a believer

English translation · Sunan Abu Dawud