4:94
O you who believe[d]! When you go forth in (the) way (of) Allah then investigate, and (do) not say to (the one) who offers to you (a greeting of) peace, "You are not a believer," seeking transitory gains (of) the life (of) the world, for with Allah (are) booties abundant. Like that you were from before, then conferred favor Allah upon you; so investigate. Indeed, Allah is of what you do All-Aware.