For they bear not the sword in vain, etc. It is another part of the office of magistrates, that they ought forcibly to repress the waywardness of evil men, who do not willingly suffer themselves to be governed by laws, and to inflict such punishment on their offenses as God's judgment requires; for he expressly declares, that they are armed with the sword, not for an empty show, but that they may smite evil-doers.
And then he says, An avenger, to execute wrath, 1 etc. This is the same as if it had been said, that he is an executioner of God's wrath; and this he shows himself to be by having the sword, which the Lord has delivered into his hand. This is a remarkable passage for the purpose of proving the right of the sword; for if the Lord, by arming the magistrate, has also committed to him the use of the sword, whenever he visits the guilty with death, by executing God's vengeance, he obeys his commands. Contend then do they with God who think it unlawful to shed the blood of wicked men.