By their fruits you will know them. This is not to be understood as the external fruits of life, for on occasion false teaching and outwardly impeccable behavior exist together while, conversely, healthy, wholesome teaching and a wicked life can exist together as well, of which Judas, Christ’s betrayer, is an example. Instead, one must distinguish the fruits of doctrine in and of themselves, whether they are good or evil, as is explained in Luke 6:43-44. If the fruits of doctrine are good, then the doctrine is also good; if they are bad and destructive, then the doctrine is also destructive and misleading.
Each and every Christian must be on guard against false prophets. First and foremost, church teachers must be alert and warn the gullible against them. This is why the Lord God has placed the teachers as shepherds and watchmen (Acts 20:28 and Ezekiel 3:17).
Each Christian, in his own right, must be vigilant against false prophets so that he will not follow them. For the Lord is not speaking here to His disciples only, but, as is evident in the beginning of Matthew 5, to all people. He admonishes them all to beware of false prophets. In like fashion in 1 John 4:1 John exhorts: “Beloved, do not believe in every spirit, but test whether the spirits are from God, for many prophets have gone out into the world.” And in 1 Thessalonians 5:21 St. Paul says: “Test all things, and keep what is good.”
The Christian Church is the true Ark of Noah; those who remove themselves from it must suffer eternal destruction. The Christian Church is the sole sheepfold of the Lord; whichever little sheep runs away from it will certainly fall into the jaws of the wolf of the soul, the devil. The man who does not have the Church as his spiritual mother cannot have God as his Father.
One cannot come into the Church Triumphant, into the flock of the elect, unless one first comes from the Church Militant, from the true Church in this life. For this all hangs indivisibly together: the Lord God, His holy Word, right faith, true Church, and eternal salvation. Whoever has the one has all of them together; whoever loses one has lost them all. Therefore, each of us must be on guard with the utmost assiduousness so that we are not led away from God’s Word and the true Church by false prophets.
False prophets must be those who falsify God’s Word by human opinion, by their own inner thoughts, or by deviating from it in some other way. It follows from this that all teaching must be tested and judged according to Scripture. For in holy Scripture the Lord God has clearly and fully revealed what is necessary for our salvation.
If a simple Christian replies that it is too much and too difficult for him to judge all doctrine by Scripture, then let him be aware that the Lord God not only instituted the preaching ministry for his benefit but also the beloved Catechism, in which he can find the principal articles of the Christian religion set forth. You see, if in Christian innocence he holds to this and rejects all teachings that contradict it, then he will carry on in safety. And this is the test of false doctrine, namely, Scripture.
All doctrine is aimed at the benefit and consolation of mankind. Thus, the further conclusion is that whenever a teaching is in accord with God’s Word, its purpose is God’s glory and man’s well-being. Such teaching is also good, and those who proclaim it are good prophets. Conversely, whenever a teaching does not correspond to God’s Word its purpose is not for God’s glory nor man’s consolation; it is false and those who proclaim it are false prophets.
Everything a man can know, regardless of what it may be, whether it be art, wisdom, and knowledge – even if he were equal to Solomon and were expert in all Scripture and all other human endeavors and willing to sacrifice life and limb – without true love and a true Christian heart he is nothing. This is why a simple layman, in whom true faith is working through pure love, is more pleasing to God than a great scholar in whom there is mere knowledge without love or humbleness. Thus, St. Paul says in Ephesians 3:19 that”…loving Christ is better than all knowledge.”