Аль-Анфаль 8:61

Islam relies not on the use of force but on the demonstration of force to inspire awe in the enemy. That is why the believers were commanded to equip themselves with power so that the enemy might be demoralized and refrain from aggression. Those who spend their resources in strengthening Islam intellectually and materially will be rewarded many times over by their Lord. The secret of success in Islam does not lie in military confrontation but in the preaching of its principles—hence the command that whenever there is an offer of peace by the other party, it should be accepted, setting aside every doubt or suspicion, because doubt or suspicion is in any case an uncertain thing, but the benefit of a cease-fire is certain: it permits the dawah work of Islam to start in a peaceful atmosphere. The stoppage of war thus facilitates the ideological expansion of Islam. Islam in itself is the greatest power. If the belief in God and the Hereafter is engendered in a group, then all those psychological drawbacks which cause differences and clashes are driven out of them. Thereafter, it necessarily happens that all of them join together and become one, and it is a fact that the greatest strength lies in unity. A united group, though small, will overcome a group larger than itself. Mutual integration is the most difficult task. The sign of a divinely—aided group is that its members are united; nothing succeeds in disuniting them.