Musannaf Ibn Abi Shayba 37:556

Ibn Idris narrated to us, from Hisham, from Ibn Sirin, who said: Zayd ibn Thabit came to Uthman. He said: "These Ansar are at the door. They say: 'If you wish, we will be Ansar (helpers) to Allah twice.'" He (Uthman) said: "As for fighting, then no."