Al-Anfal (The Spoils of War)
Surah 8 · Verse 43
And (remember) when Allah showed them less in your dream, and had He showed them numerous you would have become weak hearted and you would have disputed about the affair, but Allah kept you safe, He is certainly the Knower of that which is in the hearts,
The Muslims must have seen 626 infidels instead of 313 because in 3:13 it is stated that they saw twice their number, still it was less than their actual number. Muslims seeing lesser number of infidels must have been encouraged but infidels must have felt miserable to have been defeated by a very less number of Muslims.
