Now, who are the ones that trample on what is holy and turn against us? This, too, happens in two areas, both in doctrine and in life. In the first place, it is the false teachers that do it. They take our Gospel and learn it; thus they get our jewel and precious treasure in which we are baptized and live and of which we boast. Then they go back where they came from and start preaching against us and turning their snouts and their teeth against us. Our sectarian fanatics used to keep very quiet when the pope was raging and ruling, and you never heard a peep out of them. Now that we have run the danger of opening the path and of liberating them from the tyranny of the pope, and now that they have heard our doctrine and can imitate our preaching, they go out and turn against us. They become the worst enemies we have on earth, and no one has ever preached as badly as we, though without us they would not have known anything about it. (Luther’s Works, v. 21, pages 224).

Matthew 7:6. Do not give dogs what is holy; and do not throw your pearls before swine, lest they trample them underfoot and turn to attack you.

Now the Lord Christ has almost finished His preaching about the fruit and the works that follow doctrine. Next He will begin warning and admonishing us to be on our guard against other doctrine. Thus He also admonishes the apostles when He sends them out to preach, and says (Matt. 10.16): “Behold, I send you out as sheep in the midst of wolves; so be wise as serpents and innocent as doves.” The situation of a Christian who is supposed to speak and preach the Word of God and to confess it by his life is really a dangerous one, because of the people. He has good reason to become impatient, because the world is so infinitely evil and because he lives in it surrounded by snakes and all kinds of vermin. That is why He declares: “Be careful not to throw what is holy before swine and dogs, for they might trample it underfoot or turn to attack you.” By this He intends to show them and to teach them a lesson. Wherever they go to preach in public before a crowd, they will find dogs and swine, who cannot do anything but trample on the Gospel and then persecute the preachers. (Luther’s Works, v. 21, p. 223-224).