Luke 6:43-45 – “For no good tree bears bad fruit, nor again does a bad tree bear good fruit,  for each tree is known by its own fruit. For figs are not gathered from thornbushes, nor are grapes picked from a bramble bush.  The good person out of the good treasure of his heart produces good, and the evil person out of his evil treasure produces evil, for out of the abundance of the heart his mouth speaks.
Salvation by free, sovereign, electing love will always produce fruit in a person’s life. This is the consistent testimony of the Scriptures. God has chosen to save people from their sins. Sinless perfection well not become a reality this side of glory but there will be change; change of heart, attitude, direction of life, and behaviour. There will be change of desire. Salvation brings the desire to please the God who in love has reached down and rescued us. This is what Jesus has been teaching in this little section of the sermon that Luke records for us in Luke 6. A tree is known by its fruit.
But Jesus takes this very non surprising teaching to a shocking level when he states that “out of the abundance of the heart, the mouth speaks.” It pictures the heart like a container that, when it gets filled, to prevent it from bursting, has an overflow valve that allows the liquid coming into it to escape and cause less damage.
Picture that container as your heart and the overflow valve as your mouth. What comes out of that valve, your mouth, is what gets poured into the container, your heart. It is unavoidable.
You find yourself in an argument with your spouse (or someone else) and out comes an insult, a slur or an attack of some kind that just makes him/her shrivel up and surrender. And out of your mouth come the words – “I didn’t mean it”. And while you are hoping that this attempt at restitution will suffice, you hear the question “Then why did you say it?” Whatever reasons you may find in your own defense will not likely be what Jesus says here. You said it because that is what is in your heart.
We may talk about people whose mouths seem to be disconnected from their brains and their number is legion. Attached to their brains or not, they are firmly glued to their hearts, their inner being, their real motives and deep seeded beliefs. This is not easy to accept, mainly because so many of us have said some pretty harsh, hurtful, ignorant things. To conclude that that is a reflection of what is in our hearts is very convicting. It is frightening. It is horrifying. It may be why we seek to lessen the blows of what Jesus says here. Some people will just outright deny that their words come from their hearts. But they do.
We are saved by free, sovereign, electing grace. And we had better be glad that we are. Sanctification is a gradual process. We do not come to faith and get zapped with sinlessness. This is why we are told to chase after righteousness (Romans 14:9, I Corinthians 14:1, I Timothy 6:11, II Timothy 2:22). But we are told to pursue it because by His grace and power – we can.
The words that come out of our mouths are a constant call to us regarding just how sinful our hearts still are and how far we have to go in the sanctification process. But there is also this: the words that come out of our mouths are a constant reminder of just how great the grace of God was when He came and saved us; just how great it is in keeping us; just how faithful He is in loving us and just how powerful the work of the Holy Spirit is in sanctifying us.
Don’t try to wiggle your way out of the severity of these words of Jesus to His followers. See them as a gift to you about just how much you need the grace of God. See them as His call to you to get to work on even this gauge of the heart. See them as an opportunity to triumph even over the tongue and the heart. This “unruly evil” (James 3:8) can be tamed by the power of the Holy Spirit who lives in us. By His power we can have renewed hearts and therefore renewed mouths. What a work God has accomplished for us!