Sahih Muslim | Book 30 | Chapter 10

Narrated by Sa'd
Sa'd reported that on the Day of Ubud I saw on the right side of Allah's Messenger (may peace be upon him) and on his left side two persons dressed in white clothes and whom I did not see before nor after that, and they were Gabriel and Michael (Allah be pleased with both of them).

Narrated by Sa'd b. Abu Waqqas
Sa'd b. Abu Waqqas reported: I saw on the right side of Allah's Messenger (may peace be upon him) and on his left side two persons with white clothes on the Day of Uhtid fighting a desperate fight, and I saw them neither before nor after that.