Abu Dawud Book 33, Hadith Number 4441.

Narated By Al-Bara’ ibn Azib : while I was wandering in search of my camels which had strayed, a caravan or some horsemen carrying a standard came forward. The bedouin began to go round me for my position with the Prophet (PBUH). They came to a domed structure, took out a man from it, and struck his neck. I asked about him. They told me that he had married his father’s wife.