Quran 9:123 — Ultimatum (Bara'ah)

O you who believe, you shall fight the disbelievers who attack you—let them find you stern—and know that GOD is with the righteous.

[9:122] When the believers mobilize, not all of them shall do so. A few from each group shall mobilize by devoting their time to studying the religion. Thus, they can pass the knowledge on to their people when they return, that they may remain religiously informed.

[9:124] When a sura was revealed, some of them would say, "Did this sura strengthen the faith of anyone among you?" Indeed, it did strengthen the faith of those who believed, and they rejoice in any revelation.