Musannaf Ibn Abi Shayba 37:551

Yazid ibn Harun narrated to us, from Ibn 'Awn, from Muhammad ibn Sirin, who said: 'Uthman looked down upon them from the palace and said, "Bring me a man with whom I may debate the Book of Allah." So they brought him Sa'sa'ah ibn Suhan, and he was a young man. 'Uthman said, "Did you find no one to bring me other than this young man?" Then Sa'sa'ah spoke some words, and 'Uthman said to him, "Recite." Sa'sa'ah said: "Permission [to fight] has been given to those who are being fought, because they were wronged. And indeed, Allah is competent to give them victory." 'Uthman said, "It is not for you nor for your companions, but it is for me and my companions." Then 'Uthman recited: "Permission [to fight] has been given to those who are being fought, because they were wronged. And indeed, Allah is competent to give them victory," until he reached: "And to Allah belongs the outcome of [all] matters."