Muwatta Imam Malik Book of Hudud, Hadith 20
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."
حَدَّثَنِي مَالِكٌ، عَنْ رَبِيعَةَ بْنِ أَبِي عَبْدِ الرَّحْمَنِ، أَنَّ عُمَرَ بْنَ الْخَطَّابِ، قَالَ لِرَجُلٍ خَرَجَ بِجَارِيَةٍ لاِمْرَأَتِهِ مَعَهُ فِي سَفَرٍ فَأَصَابَهَا فَغَارَتِ امْرَأَتُهُ . فَذَكَرَتْ ذَلِكَ لِعُمَرَ بْنِ الْخَطَّابِ فَسَأَلَهُ عَنْ ذَلِكَ فَقَالَ وَهَبَتْهَا لِي . فَقَالَ عُمَرُ لَتَأْتِينِي بِالْبَيِّنَةِ أَوْ لأَرْمِيَنَّكَ بِالْحِجَارَةِ . قَالَ فَاعْتَرَفَتِ امْرَأَتُهُ أَنَّهَا وَهَبَتْهَا لَهُ .