Musnad Ahmad 3:69

'Affan narrated to us, Jarir ibn Hazim narrated to us, he said: I heard Muhammad ibn 'Abd Allah ibn Abi Ya'qub narrating from Rabah, he said: My family married me to a Roman slave-girl of theirs. She bore me a black boy. A Roman slave of theirs, who was called Yuhannis, became attached to her, and he began to speak to her in the Roman language, and she became pregnant. She had previously borne me a black boy like me, but she came with a boy who was like a gecko among the geckos. I said to her: "What is this?" She said: "He is from Yuhannis." I asked Yuhannis, and he confessed. I came to 'Uthman ibn 'Affan and mentioned that to him. He sent for them both and questioned them, then he said: "I will judge between you with the judgment of the Messenger of Allah, peace and blessings of Allah be upon him: 'The child is for the bed, and for the adulterer is the stone.'" He attributed him to me. He said: Then he flogged them both. She later bore me another black boy.