Malik related to me from Rabia ibn Abi Abd ar-Rahman that Umar
ibn al-Khattab spoke about a man who went out with his wife's slave-
girl on a journey and had intercourse with her and then the wife
became jealous and mentioned that to Umar ibn al-Khattab. Umar
questioned him about it. He said, "She gave her to me." Umar said,
"Bring me a clear proof or I will stone you." Rabia added, "The wife
confessed that she had given her to him."
Muwatta Malik Book 41, Hadith 22