Musnad Ahmad 612:10

Muhammad ibn Bakr—meaning al-Bursani—narrated to us, Wahib ibn Khalid informed us, Ayyub narrated to us, from Abu Qilabah, from Abu al-Ash'ath, who said: Orators stood in Iliya during the governorship of Mu'awiyah, and they spoke. The last of those who spoke was Murrah ibn Ka'b, who said: "Were it not for a hadith I heard from the Messenger of Allah (may Allah bless him and grant him peace), I would not have stood up. I heard the Messenger of Allah (may Allah bless him and grant him peace) mentioning a tribulation and bringing its time near. Then a man passed by, covered with a garment. He said: 'This one and his companions will be upon the truth and guidance on that day.' I said: 'This one, O Messenger of Allah?' And I turned his face toward him. He said: 'This one.' And behold, it was Uthman.