Quran 8:66 — The Spoils of War (Al-Anfal)

Now (that many new people have joined you) GOD has made it easier for you, for He knows that you are not as strong as you used to be. Henceforth, a hundred steadfast believers can defeat two hundred, and a thousand of you can defeat two thousand by GOD's leave. GOD is with those who steadfastly persevere.

[8:65] O you prophet, you shall exhort the believers to fight. If there are twenty of you who are steadfast, they can defeat two hundred, and a hundred of you can defeat a thousand of those who disbelieved. That is because they are people who do not understand.

[8:67] No prophet shall acquire captives, unless he participates in the fighting. You people are seeking the materials of this world, while GOD advocates the Hereafter. GOD is Almighty, Most Wise.