Musannaf Ibn Abi Shayba 27:420

Waki’ narrated to us, from Mis’ar, from ‘Imran ibn ‘Umayr, from Kulthum, who said: I heard Ibn Mas’ud saying: "I would not like to have shot ‘Uthman with an arrow"—he said: I think he meant killing him—"even if I were to have the likes of Uhud in gold."