Musannaf Ibn Abi Shayba 23:34

Ibn ‘Ulayyah narrated to us, from Hajjaj bin Abi ‘Uthman, from Yahya bin Abi Kathir, from Hilal bin Abi Maymunah, from ‘Ata’ bin Yasar, from Mu’awiyah bin al-Hakam al-Sulami, who said: I had a slave girl who used to graze my sheep in the direction of Uhud. I checked on her one day, and behold, a wolf had taken a sheep from her flock. I am a man from the children of Adam; I feel regret as they feel regret, but I struck her a blow. Then I came to the Messenger of Allah (ﷺ), and he considered that a grave matter for me. I said, "O Messenger of Allah, shall I not free her?" He said, "Bring her to me." So I brought her to him. He said to her, "Where is Allah?" She said, "In the heaven." He said, "Who am I?" She said, "You are the Messenger of Allah." He said, "Free her, for she is a believer."