Musannaf Ibn Abi Shayba 36:515

Waki’ narrated to us, from Sufyan, from ‘Abd al-Malik ibn ‘Umayr, from a freed slave of Rib’i ibn Hirash, from Rib’i, from Hudhayfah, who said: We were sitting with the Prophet, may Allah bless him and grant him peace, and he said: "I do not know how long I will remain among you, so follow those who come after me," and he pointed to Abu Bakr and ‘Umar. "And be guided by the guidance of ‘Ammar, and whatever Ibn Mas’ud narrates to you, believe him."