Have you not considered the chiefs of the children of Israel after Musa, when they said to a prophet of theirs: Raise up for us a king, (that) we may fight in the way of Allah. He said: May it not be that you would not fight if fighting is ordained for you? They said: And what reason have we that we should not fight in the way of Allah, and we have indeed been compelled to abandon our homes and our children. But when fighting was ordained for them, they turned back, except a few of them, and Allah knows the unjust.

And prepare against them what force you can and horses tied at the frontier, to frighten thereby the enemy of Allah and your enemy and others besides them, whom you do not know (but) Allah knows them; and whatever thing you will spend in Allah's way, it will be paid back to you fully and you shall not be dealt with unjustly.