John Calvin Commentary Isaiah 59:17

"And he put on righteousness as a breastplate, and a helmet of salvation upon his head; and he put on garments of vengeance for clothing, and was clad with zeal as a mantle." — Isaiah 59:17 (ASV)

And he put on righteousness as a coat of mail. Here he equips God with his armor, for the purpose both of confirming more and more the confidence of believers, and of stripping all men of all confidence in their own strength. The meaning of the verse amounts to this: that God lacks nothing for defeating his enemies and gaining the victory, because from his righteousness, power, and grace, and from his ardent love for his people, he will make for himself πανοπλίαν—complete armor.

This is also worth noting; for, although we acknowledge that God is sufficiently powerful, yet we are not satisfied with it, but at the same time seek other help. Thus our minds are always inclined to unbelief, so that they fasten on inferior means, and are greatly entangled by them.

To correct this vice, Isaiah presents this lively description, as if he had said, “Know that God has in his hand all the safeguards of your salvation, and will lack nothing to deliver you despite enemies and bring you back to your native country; and therefore there is no reason why you should tremble.” Besides, there is nothing we are more prone to than to imagine that we bestow something on God, and thus to claim for ourselves some part of the praise which ought to remain his, undivided.

When he clothes God with vengeance, and with indignation as a cloak, this relates to enemies, against whom God is said to be enraged for the sake of his people. And thus, the more that Satan labors and makes every effort against us, so much the more does God kindle with zeal, and so much the more powerfully does he rise up to assist us. Although, therefore, Satan and all the reprobate do not rest, but raise up obstacles of every kind to prevent our salvation, and even exert themselves furiously to destroy us, yet, by his power alone, God will defeat all their efforts.