Musannaf Ibn Abi Shayba 28:1079

Waki’ narrated to us, Hasan bin Salih narrated to us, from al-Suddi, from ‘Adi bin Thabit, from al-Bara’ bin ‘Azib, who said: I met my maternal uncle and he had the banner with him. I said to him, "Where are you heading?" He said, "The Messenger of Allah (ﷺ) sent me to a man who married his father’s wife after him, so that I may kill him or strike his neck."