Matthew 5:18. For truly, I say to you, till heaven and earth pass away, not an iota, not a dot, will pass from the Law until all is accomplished.
That is to say: “I want it to be taught and held pure and whole, without the least subtraction.” This is an indication that He found a far different situation, one in which neither doctrine nor life was in good condition. Therefore, as we shall see, He must take up both of these and salt them through to purify them. We have to teach the same way; we do not permit a single letter to be subtracted from the Gospel, but we say that it all has to be taught, believed, and kept pure. Thus He indicates that He is going to preach a sharp sermon. He will not let them get away with the accusation that He intends to abolish the Law. Instead He will turn the attack back upon them by proving that they have weakened and abolished the Law with the glosses they have smeared over it. Our mob of papists have done the same with the Gospel and Scripture. They have completely ignored that most important doctrine, the righteousness of faith through Christ. They have removed one kind from the Sacrament and have concealed the words of the Sacrament. In fact, they have had the audacity to take the commandments which Christ lays down here and to preach them as bits of good advice rather than as necessary commandments, in direct opposition to the word and stipulation that heaven and earth have to pass away before even the least of these could be left unobserved. Now He immediately passes serious judgment upon such preachers:
Matthew 5:19. Whoever, then, relaxes one of the least of these commandments and teaches men so, shall be called least in the kingdom of heaven; but he who does them and teaches them shall be called great in the kingdom of heaven.
“I will make this very strong,” He says. “Not only will I not abolish them. But if any preacher relaxes or ignores the tiniest part, he should know that he is no preacher of Mine, but is damned and excluded from the kingdom of heaven.” The phrase “shall be called least in the kingdom of heaven” means simply that he shall not be in the kingdom of heaven, but that, as he considers it a trifle to despise God’s command, so he also shall be despised and rejected.
The preachers of the Gospel must all be ready to make the same claim before the whole world, and we challenge our opponents to show us one passage or article of Scripture which we abolish or do not preach correctly. At the Diet of Augsburg they themselves had to testify that our confession is purely Scriptural and does not conflict with any article of faith. All they are shouting about is the fact that we do not also hold to the additional things that have been decreed for them by the councils and the popes; we are supposed to be damned because we want no part of their foul maggots and tawdry human baubles. Nevertheless we have always expressed our willingness to get along with them. We still could, too, if they would grant this much: that these things are free and optional, neither necessary for salvation nor contrary to the Gospel; that a person may participate in them or not as he pleases, as he may in any other free and nonobligatory thing that neither helps nor hinders us, the way a person takes part in the activities during a carnival. But this concession they will not make. So we cannot do otherwise. For the sake of their worthless and useless rot, we cannot surrender Christ our Savior, who through His dear suffering and death has shown and given us more kindness than the pope, Francis, Dominic, or any saint. If they let us keep Him, we would be willing to observe everything that they would impose upon us, and do so better than they do themselves.
Since they are not satisfied with this, but want to make us forsake Christ and pure doctrine which they themselves cannot criticize, we repudiate them. Christ condemns and rejects them, both their doctrine and their life, as men who not only relax God’s Word and commandment but absolutely nullify it by such shameless teachings as these: that it is not necessary to love God with all your heart; that a person is honoring his parents if he decides to enter a monastery or gives the church the money he might have used to support his parents; that a man may desert his betrothed to enter a monastery. In short, everything that the Lord demands here on the basis of God’s command they have made nonobligatory, as if these were merely bits of good advice or works of supererogation.
From all this you can tell what wonderful Christian teachers and holy people these men are! They brashly dare to abolish and abrogate all of God’s commandments, and do so with impunity. Of us, meanwhile, they demand with violent threats that we acknowledge the necessity of their man-made trifles. When we refuse to accept and support these, they attack us with horrible edicts and every kind of fury. Figure out for yourself what Christ will say to all this, since here He pronounces the severe judgment that a man shall have no part in His kingdom if he breaks even the least commandment while teaching and keeping all the others exactly. Where do you think they belong but in the deepest fire of hell? Never has there arisen such a shameful race on earth who dealt so impudently with the Word of God against their own better knowledge, while they still laid claim to the title “Christian leaders.” So beware of them. Let no one be scared by their damnation, persecution, and madness. Here we have the assurance that those who teach God’s Word purely and truly and cling to it shall be great before Christ in the kingdom of heaven in spite of the fact that this mob may curse them to the lowest hell.
I shall not go into the question now of how the Law is to be fulfilled so that no iota or dot of it is lost, though at the same time we teach that no man can fulfill it. I have said that here Christ is not talking primarily about life, but about doctrine. He is not dealing with the great chief doctrine of what He is and what He gives us. We cannot be justified or saved through the teaching of the Law, which only brings us to the knowledge of ourselves, the knowledge that by our own ability we cannot properly fulfill an iota of it. Once we have become Christians through Baptism and faith, we do as much as we can. Still we can never take our stand before God on this basis, but we must always creep to Christ. He has fullfilled it all purely and perfectly, and He gives Himself to us, together with His fulfillment. Through Him we can take our stand before God, and the Law cannot incriminate or condemn us. So it is true that all must be accomplished and fulfilled even to the smallest dot, but only through this one Man. About this we have said enough elsewhere.
Luther, M. (1999, c1956). Vol. 21: Luther's works, vol. 21 : The Sermon on the Mount and the Magnificat (J. J. Pelikan, H. C. Oswald & H. T. Lehmann, Ed.). Luther's Works (21:70). Saint Louis: Concordia Publishing House.