John Calvin Commentary Isaiah 9:5

"For all the armor of the armed man in the tumult, and the garments rolled in blood, shall be for burning, for fuel of fire." — Isaiah 9:5 (ASV)

For every battle. Here commentators nearly agree that Isaiah intended to contrast the victory that God was about to give to his people with other victories. Others conquer by making a great slaughter of their enemies, but here the Lord will conquer by his own hand alone. He expresses more fully what he had said, As in the day of Midian (Isaiah 9:4). The Lord therefore, he says, will not employ the agency of a great multitude, but will achieve a victory for himself from heaven. When the Lord acts by himself, every covering is removed, and we perceive more clearly that he is the Author of our life and salvation.

Now, since there is a contrast that expresses the difference between the ordinary mode of warfare and the miracle of redemption, the copulative ו, (vau), in the middle of the verse, should be rendered but; as if he had said, that it is usually amidst the confusion of the battle that enemies are hewn down: but God will act in a very different manner, for he will destroy the enemies of the Church, as if he sent down lightning from heaven, or suddenly struck them with thunderbolts. It may perhaps be thought better to adopt the opinion of those who explain the second clause as a continuation of the first, that all warriors will be with trembling and with burning fire. But the former meaning is more appropriate, and is likewise supported by the words of the Prophet. Hence it is evident that the present subject is not merely the deliverance that the people obtained from Cyrus, permitting them to return to their native country, but that these words must be viewed as extending to the kingdom of Christ.