Mark 7:15 "It's not what goes into your body that defiles you; you are defiled by what comes from your heart."
Jesus had been conversing with Pharisees who were critical of his disciples for not following their traditions for hand washing to ceremonially cleanse themselves. He explained that their concerns for cleaning the outside of the body were misplaced. The real uncleanness comes from within. Apparently the problem with men is the problem within each man. We have hearts that have seeds of sin that germinate within. Since the beginning...since the first man, Adam, the tendency to "go wrong" is right there in the center of each of us. So the answer to that problem can't be addressed from the outside-in...it must come from the inside-out. We need the spiritual surgeon's scalpel of God's word to go to the source. The Pharisees' sin was to cancel the effect of God's word by substituting their own words and their own ways. Our deception comes when we believe that we are o.k. and that we are essentially good and that we are essentially clean within. We need the help of the Lord to understand that we are unclean within. Here are some amplifying words from Jesus (verse 20): "It is what comes from inside that defiles you. For from within, out of a person's heart, come evil thoughts, sexual immorality, theft, murder, adultery, greed, wickedness, deceit, lustful desires, envy, slander, pride, and foolishness. All these vile things come from within; they are what defile you."
Listen once more to Jesus as he later instructed the disciples: (John 15:3) "Now you are clean through the word which I have spoken to you."