Musannaf Ibn Abi Shayba 27:515

Abu Usama narrated to us, he said: Mis'ar narrated to us, from Sa'd ibn Ibrahim, from his father, from Sa'd, who said: I saw on the right of the Messenger of Allah, may Allah bless him and grant him peace, and on his left, on the day of Uhud, two men wearing white garments, whom I had not seen before nor after—meaning Gabriel and Michael.