What does Matthew 7:17 mean?
Jesus is warning His listeners to beware of false prophets. They may look like sheep, but they're actually hungry wolves. The way to properly identify them is by their fruit: what grows from their lives and teaching. Grapes don't grow on thorn bushes, and figs don't spring from thistle plants (Matthew 7:15–16). In the same way, legitimate spiritual fruit (Galatians 5:22–24) comes from a true believer.Christ clarifies that point even further, here. Healthy trees bear good fruit, sick trees bear bad fruit. That law of nature is true of people, as well as trees. "Healthy" prophets and teachers demonstrate through their lives and character that they are authentic messengers of God (1 John 4:1).
Jesus' words here are close to what John the Baptist said to the Pharisees: "Bear fruit in keeping with repentance" (Matthew 3:7–8). Jesus has also challenged the teaching and practice of the Pharisees throughout the Sermon on the Mount (Matthew 5:20).