(18) باب {إِذْ هَمَّتْ طَائِفَتَانِ مِنْكُمْ أَنْ تَفْشَلاَ وَاللَّهُ وَلِيُّهُمَا وَعَلَى اللَّهِ فَلْيَتَوَكَّلِ الْمُؤْمِنُونَ}
Narrated Sa`d bin Abi Waqqas:
I saw Allah's Messenger (ﷺ) on the day of the battle of Uhud accompanied by two men fighting on his behalf. They were dressed in white and were fighting as bravely as possible. I had never seen them before, nor did I see them later on.
Reference: Sahih al-Bukhari 4054
In-book reference: Book 64, Hadith 100
USC-MSA web (English) reference(deprecated numbering scheme): Vol. 5, Book 59, Hadith 384