What does Matthew 7:19 mean?

Jesus is warning His listeners, followers, and disciples to beware of false prophets. The term "false prophet" most literally applies to anyone who claims to speak on behalf of God, when they do not. The warnings against false prophets also apply, in broad terms, to anyone who promotes deceptive or errant spiritual claims. In part—and certainly for His original audience—Jesus is warning against the teaching of the Pharisees and Israel's other religious leaders (Matthew 5:20). They are the ones who lead their followers on the wide path that leads to destruction. Jesus' path is hard, but it leads to life (Matthew 7:13–14).

Now Jesus directly echoes what John the Baptist said to a group of religious leaders, Pharisees and Sadducees, who came to see him in the wilderness. After calling them a "brood of vipers," John commanded them to "Bear fruit in keeping with repentance." Then he warned them: "Even now the axe is laid to the root of the trees. Every tree therefore that does not bear good fruit is cut down and thrown into the fire" (Matthew 3:7–10).

Diseased trees, Jesus has said, bear bad fruit. The only thing they are good for is to become fuel for fire. Jesus' mention of fire is meant to refer to the eternal fires of hell and separation from God. False prophets and false religious leaders that do not live what they teach and lead others in the wrong direction are like sick trees. They will be burned (John 15:1–6).