When Uthman (may Allah be pleased with him) was appointed caliph, Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) set out from Madinah for Kufah. He praised and extolled Allah, then said: "To proceed: The Commander of the Believers, Umar bin al-Khattab (may Allah be pleased with him), has died, and we have never seen a day with more sobbing than that day. We, the Companions of Muhammad (peace and blessings be upon him), gathered and spared no effort in choosing the best and most upright of us, and we pledged allegiance to him. So you too pledge allegiance to the Commander of the Believers, Uthman bin Affan (may Allah be pleased with him)."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 8804