Musnad Ahmad 658:154

'Abd al-Razzaq narrated to us, Ma'mar narrated to us, from Ash'ath, from 'Adi ibn Thabit, from Yazid ibn al-Bara', from his father, who said: My uncle met me while he had a banner with him. I said: "Where are you heading?" He said: "The Prophet, peace and blessings of Allah be upon him, sent me to a man who married his father's wife, and he commanded me to kill him."