Musannaf Ibn Abi Shayba 37:554

Abu Usama narrated to us, from Hisham, from his father, from Ibn al-Zubayr, who said: I said to Uthman on the day of the House (al-Dar): "Go out and fight them, for you have with you those whom Allah has granted victory with fewer than them, and by Allah, fighting them is lawful." He said: He refused and said: "Whoever owes me hearing and obedience, let him obey Abdullah ibn al-Zubayr." And his command was (followed) on that day, and he was fasting on that day.