Sayyiduna Mu'awiyah bin al-Hakam al-Sulami (may Allah be pleased with him) said: I said to the Prophet (peace and blessings be upon him): "I had a slave girl who used to graze some sheep in the direction of Uhud. Once I looked in on her and saw that a wolf had taken one of the sheep. I too am from the children of Adam; I get angry just as others get angry, so I gave her a slap." the Messenger of Allah (peace and blessings be upon him) took this very seriously. I said: "Shall I not free her?" He (peace and blessings be upon him) said: "Bring her to me." So I brought her, and he (peace and blessings be upon him) asked: "Where is Allah?" She said: "In the heaven." He (peace and blessings be upon him) asked: "Who am I?" She said: "The Messenger of Allah." He (peace and blessings be upon him) said: "Free her, for she is a believer."
Hadith Referenceالمعجم الكبير للطبراني / باب الميم / 16987