John Calvin on Deuteronomy 32:41

41 If I whet my glittering sword. The conditional particle does not leave the matter doubtful, or in suspense, but must be resolved into an adverb of time; as though He had said, As soon as He should take up arms, the destruction of the enemies would be certain; not indeed that God wants arms for the overthrow of His enemies; just as when He adds directly afterwards, “When my hand shall have taken hold of judgment,” He does not mean that it ever is taken away from Him, or escapes Him, but He thus designates its present and manifest operation. “C’est pour signifier un effet present et manifest, lequel n’estoit point apparu devant;” it is to signify a present and manifest effect, which had appeared before. — Fr. Since, therefore, God, when He spares His enemies, seems, as it were, to have thrown aside His weapons, and to be at rest, having ceased to execute the office of judge, He declares that His arms shall be ready wherewith to destroy His enemies; and again, that then He will once more take upon Him the judgment which He had seemed to lay aside; in which words He indirectly animadverts upon the foolish security of those who conceive that His power is annihilated, unless He openly exerts it, and that the judgment which He postpones is altogether extinct.