You will know them by their fruits. Grapes are not gathered from thorn bushes, nor figs from thistles, are they? So, every good tree bears good fruit, but the bad tree bears bad fruit. A good tree cannot produce bad fruit, nor can a bad tree produce good fruit. Every tree that does not bear good fruit is cut down and thrown into the fire. So then, you will know them by their fruits. (Matthew 7:16–20)

After warning about false prophets in Matthew 7:15, Jesus tells us what to watch for in identifying them. Because they are so extremely deceptive and dangerous—ravenous spiritual and moral wolves in sheep’s clothing—the Lord would hardly have left us without means of determining who they are.

Jesus assures us that we “will know them by their fruits.” A fruit tree may be beautiful, decorative, and offer pleasant shade in the summer. But its primary purpose is to bear fruit, and it is therefore judged by what it produces and not by how it looks.

There is no need to be deceived if we look closely. It is the cleverly deceptive false prophet that Jesus is speaking about here. No one needs help in deciding that a tree is bad if it bears shriveled, discolored, and obviously rotten fruit—or no fruit at all. It is the tree that appears to bear good fruit, but does not, that is deceptive.

On the other hand, it is possible for grapes to be stuck on thorn bushes and for figs to be stuck on thistles. From a distance they might appear to be growing on real fruit trees. Because the fruit is genuine, naive persons might conclude that the tree itself also has to be genuine. But in the end, a person’s basic character—his inner motives, standards, loyalties, attitudes, and ambitions—will eventually show through in what he does and how he acts.

As with everything that is godly and righteous, true fruit bearing begins on the inside, in the heart. Paul speaks of our “having been filled with the fruit of righteousness which comes through Jesus Christ” (Philippians 1:11) and informs us that “the fruit of the Spirit is love, joy, peace, patience, kindness, goodness, faithfulness, gentleness, self-control” (Galatians 5:22–23).

A person who belongs to Jesus Christ and who is called by God and given God’s message will give evidence of good fruit both in his attitudes and his actions. A person who does not belong to God, especially a false prophet who claims to be God’s messenger, will sooner or later manifest the bad fruit that the bad tree of his sensual life inevitably produces.

False prophets can disguise and hide their bad fruit for a while with ecclesiastical trappings, biblical knowledge, and evangelical vocabulary. They can cover it by belonging to Christian organizations, associating with Christian leaders, and by talking about divine things. But how they talk, act, and react when not in the view of Christians will eventually expose their true loyalty and convictions. What is in the heart will emerge, and corrupt theology will result in a corrupt life. False teaching and perverted living are inseparable, and eventually will become manifest.

Martyn Lloyd-Jones wisely comments:

A Christian can generally be known by his very appearance. The man who really believes in the holiness of God, and who knows his own sinfulness and the blackness of his own heart, the man who believes in the judgment of God and the possibility of hell and torment, the man who really believes that he himself is so vile and helpless that nothing but the coming of the Son of God from heaven to earth and His going to the bitter shame and agony and cruelty of the cross could ever save him, and reconcile him to God—this man is going to show all that in his personality. He is a man who is bound to give the impression of meekness, he is bound to be humble. Our Lord reminds us here that if a man is not humble, we are to be very wary of him. He can put on a kind of sheep’s clothing, but that is not true humility, that is not true meekness. And if a man’s doctrine is wrong, it will generally show itself at this point. He will be affable and pleasant, he will appeal to the natural man, and to the things that are physical and carnal; but he will not give the impression of being a man who has seen himself as a hell-bound sinner, and who has been saved by the grace of God alone.

Next time we’ll consider what bad fruit actually looks like and discuss the pathology of a false teacher.