Umar bin al-Hakam said: I came to the Messenger of Allah (peace and blessings be upon him) and said: O Messenger of Allah! A slave girl of mine used to graze my sheep. I came to her and a sheep from the flock was missing, so I asked her about it, and she said: The wolf ate it. I was grieved over it, and I am one of the children of Adam, so I slapped her face; and I owe (the freeing of) a neck (slave). Shall I free her? The Messenger of Allah (peace and blessings be upon him) 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: "Then free her." Umar bin al-Hakam said: O Messenger of Allah! There are things we used to do in the Jahiliyyah: we used to go to soothsayers. The Prophet (peace and blessings be upon him) said: "Do not go to the soothsayers." Umar said: And we used to take evil omens. He said: "That is only something one of you finds in himself, so let it not harm you."
Al-Shafi'i (may Allah have mercy on him) said: The man's name is Mu'awiyah bin al-Hakam; this is how al-Zuhri and Yahya bin Abi Kathir narrated it.
The Shaykh (may Allah have mercy on him) said: This is how a group narrated it from Malik bin Anas (may Allah have mercy on him), while Yahya bin Yahya narrated it from Malik accurately, saying: from Mu'awiyah bin al-Hakam; and at its end he said: He said: "Free her, for she is a believer."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الظهار / 15266