Musannaf Ibn Abi Shayba 28:1085

Hafs ibn Ghiyath narrated to us, from Ash'ath, from 'Adi ibn Thabit, from al-Bara' ibn 'Azib, who said: The Messenger of Allah (may Allah bless him and grant him peace) sent [someone] to a man who had married his father's wife, and he ordered him to bring him his head.