From within, out of men's heart, come evil thoughts, sexual immorality, theft, murder, adultery, greed, malice, deceit, lewdness, envy, slander, arrogance and folly. All these evils come from inside and make a man unclean.
These thoughts matter, according to Jesus. Because evil doesn't just come out of nowhere. It lives in every human heart, regardless of whether we act on it or not. And if we're tempted to think that we are good people because we never act on our bad thoughts, it's worth wondering: what kinds of things would we do if we knew there would be no negative consequences for us? How many times have we been kept from doing something we wanted to do only because we were afraid that God or society or the law would punish us, or because our friends would think of us as bad people? How often do we do "the right thing" not because we love to do it, but simply because we don't want to be seen doing "the wrong thing"?
Because God is infinitely worthy of our love, our rejection of Him - this "sin" that is so deeply ingrained in every human heart - is infinitely horrifying. Despite His goodness to us, we have deliberately dedicated our whole lives to putting ourselves, or other things, in His rightful place.
-Paul Williams and Barry Cooper (If You Could Ask God One Question)