"A good tree does not bear rotten fruit, nor does a rotten tree bear good fruit. For every tree is known by its own fruit. For people do not pick figs from thorn bushes, nor do they gather grapes from brambles. A good person out of the store of goodness in his heart produces good, but an evil person out of a store of evil produces evil; for from the fullness of the heart the mouth speaks. "Why do you call me, 'Lord, Lord,' but not do what I command? I will show you what someone is like who comes to me, listens to my words, and acts on them. That one is like a person building a house, who dug deeply and laid the foundation on rock; when the flood came, the river burst against that house but could not shake it because it had been well built. But the one who listens and does not act is like a person who built a house on the ground without a foundation. When the river burst against it, it collapsed at once and was completely destroyed." (Lk 6:43-49)
Tree on its own has no relevance and meaning and appreciation (in this parable). Its meaning is seen only through the fruit it produces. Fruit is the indicator of the tree and its goodness. Similarly the man also has his appreciation and relevance only in his actions. Jesus here in this parable challenges the hearer to change his way of life to enter into the kingdom.
The next parable is much more challenging than the one gone before. Listening to true wisdom and not putting it into practice is like building without foundation. Jesus preaching about the kingdom and his message about the Father or from the Father are the foundations on which the listeners are asked to build their own life.
As the kingdom is preached the danger of destruction and the presence of the evil or the chaos (river burst) is at hand. Anyone who is not based on the wisdom of the kingdom of God or the wisdom of Jesus is bound to be challenged by the negative forces. Here the choice is between the wisdom of Jesus or the destruction.