Musnad Ahmad 658:140

Asbat narrated to us, he said: Mutarrif narrated to us, from Abu al-Jahm, from al-Bara’ ibn ‘Azib, who said: "I was searching for camels of mine that had gone astray during the time of the Messenger of Allah, may Allah bless him and grant him peace. I was wandering among the dwellings when I came upon a group of riders and horsemen. They arrived and circled around my courtyard, then they brought out a man. They did not question him, nor did they speak to him, until they struck his neck. When they had gone, I asked about him, and they said: 'He had consummated marriage with his father’s wife.'"