Peace be upon you and the mercy of Allah.
This occurred in the Battle of Hunayn.
It has been narrated in sources of the general public that Sa'd saw on the day of Uhud two men wearing white garments whom he had never seen before or after — referring to Gabriel and Michael — fighting fiercely. [Musnad Ahmad, Hadith 1471].
This narration may be valid; there is no verse that mentions the descent of troops as being unseen on the day of Uhud. If this narration had been reported on the day of Hunayn or Badr, we would have rejected it for contradicting the Quran, which states that Allah sent down troops that the Muslims did not see.
May you be successful in all good.