Musnad Ahmad 1034:44

Ishaq ibn Sulayman narrated to us, Kathir Abu al-Nadr narrated to us, from Rib'i ibn Hirash, who said: I went to Hudhayfah in al-Mada'in during the nights when the people were marching toward Uthman. He said: "O Rib'i, what have your people done?" I said: "About which of their affairs are you asking?" He said: "Those of them who went out to this man." I named some men among those who went out to him. He said: "I heard the Messenger of Allah, peace and blessings of Allah be upon him, say: 'Whoever separates from the community and holds the leadership in contempt shall meet Allah while having no face before Him.'"