Luke 6: “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.
Coming to faith in Jesus Christ results in a change of heart. Paul will phrase it as becoming a new creature with the old things gone and new things come (II Corinthians 5:17). Peter will talk about the new birth having purified our souls so that we can love one another sincerely and obey the truth (I Peter 1:22-23). When a believer sins such texts can be a knife to the heart. We are prone to excuse our sins and when the Bible tells us that faith in Jesus results in changed lives it is very convicting.
But change does not mean sinlessness. We must never excuse sin but we must realize that we are not saved because we are good. We have been saved by grace, are being saved by grace and will be saved by grace. It is necessary that the tension remain. We will never lives as righteously as is required by God, for what God requires is sinless perfection and only Jesus did that. That is what makes the Gospel such a marvel. He who committed no sin became sin for us that we might be the righteousness of God (II Corinthians 5:21). When we believe, that faith is credited to us as righteousness. We are not righteous. We are still sinners. But because we believe in Jesus Christ and have come to Him as our only hope, God counts us as righteous.
Some will say that if that is true then people can live like the devil and still be confident of an eternity with Christ. Ah, not so. Or as Paul puts it in Romans 6:1, “By no means!” When Paul said that he had just finished a lengthy explanation of the Gospel (Romans 1:18 – 5:21). Paul knows that an accurate explanation of the Gospel will lead people to ask “Then can we sin to make grace look more amazing?” “Not at all”, Paul replies.
What we need to remember is that the Gospel is not just us changing our minds about Jesus. It is, in the words of Romans 1:16-17, the power of God. When we come to faith in Christ, it is because God has already done something. Real change has taken place. We have been baptized into the death of Christ. We have died to the power of sin. We can now say no to sin and that is what we will want to do. No real Christian will be content to say that since he has come to Christ he can now live a reprobate life. When we come to faith in Christ we died to sin and were raised to newness of life. We are new creatures. The Holy Spirit now lives in us and the fruit of the Spirit is (not should be, could be, might be,) love, joy, peace, patience, kindness, goodness faithfulness, gentleness and self control. By the indwelling Spirit we put to death the deeds of the flesh (Romans 8:13). The Gospel of Jesus Christ is a powerful thing. It does not just result in a change of destination. It first of all results in a change of heart, of desires, of behaviour. This is why we now can say with Paul that our sin breaks our hearts and thrusts us to Christ for help and hope (Romans 7:21-8:8). So, while we are not righteous, we are righteous.
Now then, all that was said to get to the phrase of Jesus in Luke 6:45. One of the changes that the grace of God in the heart brings is a change in speech. We’ll try again tomorrow to deal with that. For now, we revel in the marvellous work of God in bringing us to faith in Jesus. We marvel that He has taken up residence in us and we marvel that what we were once powerless to do we can now do by His power and grace. Thank God for what He has done!