When He had entered a house away from the crowd, His disciples asked Him concerning the parable. So He said to them, "Are you thus without understanding also? Do you not perceive that whatever enters a man from outside cannot defile him, because it does not enter his heart but his stomach, and is eliminated, thus purifying all foods?" And He said, "What comes out of a man, that defiles a man. For from within, out of the heart of men, proceed evil thoughts, adulteries, fornications, murders, thefts, covetousness, wickedness, deceit, lewdness, an evil eye, blasphemy, pride, foolishness. All these evil things come from within and defile a man."
Steeped in legalism and tradition, the Pharisees (and the disciples) had a difficult time understanding God's love and grace. You see, it's not what you eat or drink, or what rules and regulations you follow that make you a Christian.
Likewise, it's not the absence of any of these things that make you a better Christian. We can get so hung up on rules and regulations, on making sure others around us don't do this or that, that we lose all perspective of Jesus' words here: It's not the physical stuff in life that defiles us; it's our hearts. Your actions are merely a by-product of your heart.
The Pharisees were so caught up in their rules and regulations (a.k.a. playing church) that they totally ignored the things that really defiled their lives. I mean, look at the list Jesus gives of evil things that defile us: evil thoughts, adultery, fornication, murder, stealing, coveting, wickedness, deceit, slandering another's character, pride, and foolishness. These are the things that we should be concerned about -- issues that begin in our hearts. This list was written over 2,000 years ago and it's more relevant than ever! If our hearts are in the wrong place, our actions will follow. Our hearts need to be focused on Jesus!
Maybe you're prone to watching soap operas or questionable prime-time shows where inevitably you see people undressing and making out. What do these shows do? They plant lustful thoughts in your mind. One way you can tone down the lustful thoughts is to get rid of the lustful books and magazines, and turn off the lewd television shows you once thought were so great. Instead of letting evil thoughts control you, "be transformed by the renewing of your mind" (Romans 12:2). When thoughts come up that are lustful, sensual, and wicked, you need to say out loud, "Stop! Lord, I turn these thoughts to you." God will take those thoughts and He will bring them under control.
Don't let the enemy destroy your life, your marriage, or your relationship with your family.
Don't allow these things to defile you, all the while thinking that you're "a good person" because you don't smoke or drink or eat unhealthy foods. Don't get me wrong; it's important to take care of yourself and to be a good steward of the body that God has given you. But don't let that be your sole focus when there are so many things (as Jesus lists here) that you need to control. Have a heart that seeks after the things of the Lord.
"For though we walk in the flesh, we do not war according to the flesh. For the weapons of our warfare are not carnal but mighty through God for pulling down strongholds, casting down arguments and every high thing that exalts itself against the knowledge of God, bringing every thought into captivity to the obedience of Christ, and being ready to punish all disobedience when your obedience is fulfilled" (2 Corinthians 10:3-6).