Musnad Ahmad 3:132

'Abdullah narrated to us, Surayj ibn Yunus narrated to me, Mahbub ibn Mihraz narrated to us, from Ibrahim ibn 'Abdullah ibn Farrukh, from his father, who said: I witnessed 'Uthman ibn 'Affan, may Allah be pleased with him, being buried in his clothes, stained with his blood, and he was not washed.