Watch out for false prophets, who come to you in sheep’s clothing but inwardly are voracious wolves. 16 You will recognize them by their fruit. Grapes are not gathered from thorns or figs from thistles, are they? 17 In the same way, every good tree bears good fruit, but the bad tree bears bad fruit. 18 A good tree is not able to bear bad fruit, nor a bad tree to bear good fruit. 19 Every tree that does not bear good fruit is cut down and thrown into the fire. 20 So then, you will recognize them by their fruit.
Many members of the Palm Beach Country Club had to lobby to get Bernard Madoff to take their money for investment. His marketing strategy was to play hard to get. That worked really well along with the bogus profit statements received by those members he had already taken as clients.
Unfortunately, the only information the clients saw was paper reports from Madoff. They never tried to inspect their own stock certificates or visit the accounting office. Since there were no real stock purchases, there were no stock certificates and no need for an accounting office!
A man selling false profits is one thing, but false claims about knowing God are even worse.
As we begin this section, keep in mind R.T. Frances insight that these false prophets (7:15) are outsiders (i.e. unbelievers) pretending to be insiders. Once again, Jesus gives just one command —watch out for false prophets (7:15a) — followed by an explanation (7:15b-20).
Since prophets are not part of our landscape, the idea of false prophets is a bit elusive. In Matthews Gospel (24:11 and 24:24), false prophets mislead or deceive even true disciples. Luke 6:26 tells us that false prophets are likely to be widely praised. Peter said the false prophets would introduce destructive heresies, even to the point of denying the Master who bought them (2 Pet. 2:1).
From these references, it seems reasonable to assume that false prophets taught misleading theology, heresies, and even denied important things about Jesus. John heard Jesus words, and he warned us to test for false prophets by careful examination (1 John 4:1).
Using metaphorical language, Jesus warns that the false prophets are actually predators (voracious wolves, 7:15) disguised as prey (sheep). Then he offers a way to detect these pretenders. In doing so, Jesus switches metaphors to that of fruit-bearing plants and their fruit.
R.T. France tells us that the basic principle of the fruits-test is that trees produce only the kind of fruit which reflects their basic character, good or bad (7:17-18). R.T. France adds that the fruit Jesus wants is the life and loyalty that God expects of his people; this is the righteousness Jesus has been describing, even though the word is not used.
Evaluating fruitfulness requires the restrained but necessary judgment that Jesus described in 7:1-6. Jesus used this standard of fruitfulness when he condemned the scribes and Pharisees in Matthew 23:1-36. There Jesus exhorts the people to obey what the Pharisees and scribes taught from Moses — meaning the Law — but not to imitate them because they did not practice what they taught (23:3)!
What happens to the trees that do not produce good fruit? Jesus says they are thrown into the fire (7:19). That is the ultimate fate of outsiders pretending to be insiders.
Those who have put their faith in Jesus Christ will not fail the test of fruitfulness. After explaining how God saved us by his grace in kindness toward us in Christ Jesus (Eph. 2:7), Paul explains that we have been created in Christ Jesus for good works that God prepared beforehand that we may do them (Eph. 2:10). The Holy Spirit enables us to do all that God wants.
The real thing
The truth is that over a period of time it is not that difficult to see the Holy Spirit at work in someones life. You will see or learn about acts of kindness, sacrificial service, and devotion to building up the church. Words are harder to weigh than deeds, but we always have the Bible to provide the truth against which teaching can be tested.
Remember Jesus warning! Not all allegedly-Christian teaching is true to Gods Word, even when you see it on the Internet, hear it on the radio or read it in a book. To evaluate a prophet, you need to see their life.
Copyright 2011 by Barry Applewhite, Plano, Texas. All rights reserved worldwide. Derived from material created for Christ Fellowship, McKinney, Texas. Used by permission.
 R.T. France, The Gospel of Matthew, The New International Commentary on the New Testament (Grand Rapids: William B. Eerdmans Publishing Company, 2007) 290.
 France, Matthew, 291.