The following is an excerpt from The MacArthur New Testament Commentary on Matthew 7:15-20.

Beware of the false prophets, who come to you in sheep’s clothing, but inwardly are ravenous wolves. You will know them by their fruits. Grapes are not gathered from thorn bushes, nor figs from thistles, are they? (Matthew 7:15–16)

After warning about false prophets, 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.

Similarly a prophet-used in this passage in the broadest sense of one who speaks for God-is judged by his life, not simply by his appearance or his words. The kind of person he really is cannot help being revealed. Some false prophets are noticeably spurious and only the most gullible person would be taken in by them. Others conceal their true nature with remarkable skill, and only careful observation will expose them for what they are. But there is a true assurance in the statement you will know them. 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.

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.

It is possible for real Christians to be taken in by false prophets. When believers are careless about study of and obedience to the Word, lazy about prayer, and uncritical about the things of God, it is easy for them to be deceived by someone who pretends to be orthodox-especially if he is pleasant, positive, and permissive. When that happens, they are in danger of becoming grapes on thorn bushes and figs on thistles. Satan loves to use God’s own people to promote his evil work, seeking, if it were possible, even to snatch them from their heavenly Father (Matt. 24:24).

It is also possible for a tree itself to bear fruit that is colorful, well formed, and attractive, but which is bitter, distasteful, and even poisonous. That kind of bad tree with its bad fruit is much harder to judge than thorn bushes that have grapes on them or thistles that have figs on them. In the second case, both the tree and the fruit appear to be genuine. What it bears has to be examined carefully to determine if it is good fruit or bad fruit. A mature believe who has developed discernment can spot the bad tree and bad fruit (Heb. 5:14).

Judging the fruit of false prophets, of course, is not nearly so easy as judging fruit in an orchard. But from Scripture we discover at least three primary tests we can apply in order to know. They are in the areas of character, creed, and converts.

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. John the Baptist told the hypocritical Pharisees and Sadducees who came to be baptized to first “bring forth fruits in keeping with repentance” (Luke 3:8). Their manner of living belied their claim that they loved and served God. When the multitude then asked John what good fruit was, he replied, “Let the man who has two tunics share with him who has none; and let him who has food do likewise” (v.11). To the tax-gatherers who asked what they should do, John said, “Collect no more than what you have been ordered to” (v. 13). John was saying that the person who is genuinely repentant and who truly trusts and loves God will also loveand help his fellow man (cf. James 2:15–17; 1 John 3:17; 4:20).

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.

It is nearly always the case that false prophets will attract avowed unbelievers as well as nominal and carnal believers. He appeals to the natural man and carefully avoids anything that is offensive to man’s proud, fallen nature. He makes a point of being attractive, likeable, and of giving no offense.

A second area in which a false prophet can be judged is that of doctrine. Superficially what he teaches may seem biblical and orthodox, but careful examination will always reveal ideas that are unscriptural and the absence of a strong, clear theology. False ideas will be taught, or at least important truths will be omitted. Frequently there will be a combination of both. Eventually the fruit will show a tree for what it is, because a good tree cannot produce bad fruit, nor can a bad tree produce good fruit.

The creed of false prophets never has a narrow gate or a narrow way. On the surface their message may sound difficult and demanding, but it will always rest on the foundation of man’s works and will therefore always be accomplishable by man’s own effort. They never reveal the depth or danger of sin and depravity, the need for repentance, forgiveness, and submission to the Lord, or the destiny of judgment, condemnation, and eternal destruction for those apart from God. There is no brokenness over sin and no longing after righteousness. They have easy answers for small problems. “They have healed the brokenness of My people superficially,” Jeremiah says, “saying, ‘Peace, peace,’ but there is no peace” (Jer. 6:14). There is no humility, no warning of judgment, and no call for repentance and a contrite heart of obedience.

They have a ready hearing among most people, because they say only what people like to hear. Just as did ancient Israel in Jeremiah’s time, people today like it that way (Jer. 5:31). They want to hear illusions, not truth. They are enamored with pleasure and fantasy and resent being confronted with anything disquieting and condemnatory. They want encouragement but not correction, positive words but not negative truth. They will accept grace as long as it is cheap grace and does not reflect against their own sinfulness, inadequacies, and lostness.

The creed of the false prophet, if he has any at all, will be vague, indefinite, and ethereal. No demanding truth will be absolute or clear-cut, and every principle will be easy and attractive.

False prophets can also be identified by their converts and followers. They will attract to themselves people who have the same superficial, self-centered, and unscriptural orientation as they do. “Many will follow their sensuality:” Peter tells us, “and because of them the way of the truth will be maligned” (2 Pet. 2:2). They have many followers because they teach and promote what the majority of people want to hear and believe (cf. 2 Tim. 4:3).

Their followers will be like them-egotistical, proud, self-centered, self-indulgent, self-willed, and self-satisfied, while being religious. They will be both self-oriented and group-oriented, but never God-oriented or Scripture-oriented.

God has not ordained false prophets, but He has ordained that they exist. Paul explains to the Corinthian church, “There must also be factions among you, in order that those who are approved may have become evident among you” (1 Cor. 11:19). False factions will act as magnets to attract others who are false. In that indirect way they will help protect true believers by partly separating the chaff from the wheat.