Deuteronomy 20:2

2And it shall be, when ye are come nigh. God commits the duty of exhortation to the priests, when the time of the conflict shall have arrived. But we gather from the expressions used that this passage is supplementary to the First Commandment, for it contains no more than that the priest should encourage the Israelites to confidence, the ground of which is declared to be the help of God in preserving and constantly protecting the Church, which He has once redeemed. Moreover, He forbids their fears not in one word only, but heaps many together, “let not your hearts faint, fear not, and do not tremble, neither be ye terrified.” By this we are reminded how difficult it is to cure that evil — fear, which in so many different ways assails and disturbs our minds, that they should not rest in God. And surely we all experience that we are troubled by such various besetments, that we have need of manifold remedies for the establishment of our faith. We must observe, too, the familiar representation of the presence of God, that He should go together with His people, to save them, viz., if they should be exposed to danger not by their own fault, but by the unjust aggression of their enemies.