Malik related to me from Hilal ibn Usama from Ata ibn Yasar thatUmar ibn al-Hakam said, "I went to the Messenger of Allah, may Allahbless him and grant him peace, and said, 'Messenger of Allah, a slavegirl of mine was tending my sheep. I came to her and one of the sheepwas lost. I asked her about it and she said that a wolf had eaten it,so I became angry and I am one of the children of Adam, so I struckher on the face. As it happens, I have to set a slave free, shall Ifree her?' The Messenger of Allah, may Allah bless him and grant himpeace, questioned her, 'Where is Allah?' She said, 'In heaven.' Hesaid, 'Who am I?' She said, 'You are the Messenger of Allah.' TheMessenger of Allah, may Allah bless him and grant him peace, said,'Free her.' "
USC-MSA web (English) reference: Book 38, Hadith 8
Arabic reference: Book 38, Hadith 1473