Lk 6:43-49
[Jesus said to his disciples,] 43“A good tree does not bear rotten fruit, nor does a rotten tree bear good fruit. 44For every tree is known by its own fruit. For people do not pick figs from thornbushes, nor do they gather grapes from brambles. 45A 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.
46“Why do you call me, ‘Lord, Lord,’ but not do what I command? 47I will show you what someone is like who comes to me, listens to my words, and acts on them. 48That 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. 49But 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.”
Building a House: Both the Matthean “Sermon on the Mount” and Luke’s “Sermon on the Plain” end with a “demonstration story” of two foundations. Scholars claim that the evangelists derive their materials from the Quelle, their common source. Luke has “rock” and “without foundation” while Matthew has “rock” and “sand.” Luke perhaps thinks that a person building “without foundation” is more plausible than a person building on sand. Luke also states a building process: the builder digs deeply and lays the foundation on rock.
“Building a house” is a metaphor of building a house of life. It involves all human activity and capacity: thoughts, speech, and practice. It begins from a person’s early education and ends only with death.
The disciple “builds his life” on Jesus. He must not be content with being a listener of Jesus; he must act on Jesus’ words. Being thus founded firmly on Jesus, he bears good fruits in words and deeds. He stands the test of time and opposition.