Musannaf Ibn Abi Shayba 18:1203

Abu Bakr narrated to us, he said: Ghundar narrated to us, from Shu'bah, from Mughirah, from Shubak, from Ibrahim, from Hani' ibn al-Nuwayrah, from Alqamah, from Abdullah, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "The most restrained of people in killing are the people of faith."