"For out of the heart come evil thoughts, murder, adultery, sexual immorality, theft, false witness, slander" (Matthew 15:19).
THE CANCER THE GOSPEL WAS MEANT TO CURE IS MUCH MORE SERIOUS THAN MANY PEOPLE ARE WILLING TO ADMIT. If we want any help at all, it is usually just with our outward behavior or our external circumstances. But the gospel proposes to help us with our character — which in the Scriptures is often called our “heart.” It is our character that produces our conduct, and so the gospel works on the cause of the problem and not just its symptoms.
Sin is any transgression of the will of God, but sin may occur at different levels, some more basic than others. We may sin by doing things “on the surface” that are not right, but these sins are the symptoms of a deeper problem: our hearts are in rebellion against God. Looking back at Matthew 15:19, Jesus said that it’s “out of the heart” that evil thoughts and sinful deeds arise. That’s where the real problem lies, and that’s what we need the most help with.
One of the most fascinating of the prophecies in the Hebrew Scriptures is Ezekiel 36:26,27, where God said, “I will give you a new heart, and a new spirit I will put within you. And I will remove the heart of stone from your flesh and give you a heart of flesh. And I will put my Spirit within you, and cause you to walk in my statutes and be careful to obey my rules.” Jews in the first century who were looking for the coming of the kingdom of the Messiah could not have done better than to be longing for the new hearts the Messiah would make it possible for them to have.
One of the most important things in life is to take responsibility for our faults. In the gospel of Christ, we are asked to take responsibility at the deepest level. If we are to be saved from our sins, we must humbly acknowledge not just that we have done sinful deeds, but that we are sinful people. Whatever sins we have done outwardly, it is from our hearts that such deeds have come. We need to be saved not just from the penalty for our sins, but from the sinfulness of being the kind of people who would do such things to begin with. Recognizing this is the first step toward repentance.
"Christ’s definition of sin penetrates far deeper than a list of sins on a membership card. It goes to our inner desire, motivations, and secret thoughts" (Erwin W. Lutzer).