There has already been a sign for you (O Jews) in the two armies that met (in combat i.e. the battle of Badr): One was fighting in the Cause of Allah, and as for the other (they) were disbelievers. They (the believers) saw them (the disbelievers) with their own eyes twice their number (although they were thrice their number). And Allah supports with His Victory whom He pleases. Verily, in this is a lesson for those who understand. (See Verse 8:44). (Tafsir At-Tabari)