Musnad Ahmad 1034:211

Muhammad ibn Bakr narrated to us, Kathir ibn Abi Kathir informed us, Rib'i ibn Hirash narrated to us, from Hudhayfah, that he came to him in al-Mada'in. Hudhayfah said to him: "What did your people do?" I said: "About which of their affairs are you asking?" He said: "Who among them went out to this man?"—meaning Uthman. I said: "So-and-so, and so-and-so, and so-and-so." He said: "I heard the Messenger of Allah, peace and blessings of Allah be upon him, say: 'Whoever departs from the community and holds the leadership in contempt shall meet Allah while having no face before Him.'"