Musnad Ahmad 3:43

Abdullah ibn Bakr narrated to us, Humaid al-Tawil narrated to us, from a sheikh from Thaqif—whom Humaid mentioned as being righteous—who mentioned that his uncle informed him: That he saw Uthman ibn Affan sitting at the second door of the Mosque of the Messenger of Allah, may Allah bless him and grant him peace. He called for a shoulder blade [of meat] and gnawed the meat off it. Then he stood up and prayed without performing ablution. Then he said: "I sat in the place where the Prophet, may Allah bless him and grant him peace, sat, and I ate what the Prophet, may Allah bless him and grant him peace, ate, and I did what the Prophet, may Allah bless him and grant him peace, did."