Musannaf Ibn Abi Shayba 35:101

Waki’ narrated to us, from Hasan ibn Salih, from al-Suddi, from ‘Adi ibn Thabit, from al-Bara’, who said: I met my maternal uncle and he had the banner with him. I said, "Where are you going?" He said, "The Prophet, may Allah bless him and grant him peace, sent me to a man who married his father’s wife, to kill him or strike his neck." And he mentioned that Abu Hanifa said: "There is nothing upon him except the prescribed punishment (hadd)."