That this is the proper division and distinction between the two kingdoms is powerfully demonstrated in the New Testament, where Christ and his agents, the apostles, observe the order of his kingdom most precisely, ruling in no other wise than with their sceptre, the word of God. With this word they teach, admonish, and censure men, and proclaim that he who accepts and believes it will be saved, while he who does not will be damned. [Mark 16:16] This is their method of government; they leave it at that and thereby their office is fulfilled. Nowhere does one find that if someone did not adhere to their doctrine and preaching but rather believed or taught some other faith, that they appealed to the secular government either to force such a person to accept their faith or else not to tolerate him. Nor does one find anywhere in the New Testament that any government that did this of its own accord was praised for it. On the contrary, Christ forbids it, as can be especially well observed in his explanation of his parable of the good seed and the tares, Matt. 13[:24-30, 37-43], where he says that the good seed are the children of the kingdom, sown by the Son of Man; the tares are the children of evil, sown by the devil; the harvest is the end of the world, the reapers the angels. He concludes that the tares should not be rooted up but rather allowed to remain, lest the wheat also be rooted up with them. For just as the tares are gathered and burned in the fire, so it will be at the end of the world: the Son of Man will send his angels, who will gather out of his kingdom all those that offend and cast into the furnace all those that work iniquity.
From this it is clear that Christ does not wish the sword of the secular government to be used to root anything out of his kingdom, but wishes rather to do combat there solely by his word until the end of the world. As the prophet Isaiah proclaims and says, Christ will do battle “with the breath of his mouth and with the rod of his lips,”* not with the sword of secular government. Here it is clearly stated that Christ himself will fight, not the secular government for him, with the rod of his mouth and with the breath of his lips, not with the sword of secular government. The prophet Daniel agrees with this and says that Antichrist (that is, all that sets itself against Christian faith and doctrine) shall be destroyed “without hand.” [Dan. 8:25] Whoever, then, seeks by secular power to defend true faith and doctrine or to drive out false faith and doctrine does nothing else than despise and mock the entire New Testament and the prophets as well. And, contrary to what Isaiah and Daniel say—that Christ will do battle in his kingdom by the breath of his mouth and that Antichrist will be destroyed without [human] hand—he also falsely maintains that the breath of Christ’s mouth does not do it and that one must accomplish it with one’s hand.
Furthermore, Christ and his apostles not only observe the order of his kingdom, they also leave the secular government completely unhindered in the possession of its kingdom. For when a man appealed to Christ to make his brother divide an inheritance with him, Christ refused in serious words saying: “Man, who made me a judge over you?” [Luke 12:14] And before Pilate he said: “My kingdom is not of this world.” [John 18:36] He also taught his disciples, saying: “The secular kings exercise lordship and the mighty are called gracious lords. But ye shall not be so!” etc. [Luke 22:25-26] From this one sees how God wishes to have the two kingdoms distinguished from one another. And since Christ remains in his kingdom and lets the secular kingdom go its own way, even though he is far mightier than all emperors and kings, it is all the more proper that the secular government should take care of its own kingdom and not attempt to govern that which belongs to Christ.
Therefore, the sum and substance of the whole matter is this, that a government that wishes to discharge its office and not claim more than has been entrusted to it should and must leave it entirely to Christ the king to determine and judge, by means of the sceptre of his divine word, whether any teaching about faith, how man may come to God and be saved, be true or false. Just as one clearly sees that in his kingdom Christ does both things, namely, teaches the true faith and condemns the false, pours the holy spirit into the heart and drives the devil out, doing both through his sceptre, the word, and calls on no secular authority to assist. Hence it is not proper for secular authority to do this. Rather it should use its sceptre or sword in the secular realm against external misdeeds, so that no one may be harmed in his body or goods. In such matters the secular sword is effective and God has established it for that reason. But the sword is of no use in forcing people to adhere to this or that faith. In the final analysis, whether you hang or drown them, the choice must still be left to those who do not want to go to heaven to go down to hell to the devil or his mother instead.
* Isa. 11:4, where the prophet actually says “with the rod of his mouth and with the breath of his lips.”