Musannaf Ibn Abi Shayba 36:67

Abu Bakr narrated to us, he said: Waki' narrated to us, from Abu Na'amah, who heard it from Khalid ibn Umayr, from Utbah ibn Ghazwan, who said: "I have seen myself with the Messenger of Allah, may Allah bless him and grant him peace, as the seventh of seven."