“Don’t you see that whatever enters the mouth goes into the stomach and then out of the body? But the things that come out of a person’s mouth come from the heart, and these defile them. For out of the heart come evil thoughts—murder, adultery, sexual immorality, theft, false testimony, slander. These are what defile a person; but eating with unwashed hands does not defile them.” Matthew 15:17-20 NIV
Evil cannot exist in a vacuum. It needs to find a place where it can mature and thrive. This evil can reside in the heart of one who does not abide in the Lord. Evil outside of someone does not make that individual impure. It is the evil that comes forth from the heart in evil actions and words. This is the message which Jesus wished to convey.
The Jewish leaders were more concerned with outward appearance than what resided within. They, therefore could not make sense of what Jesus preached. One must turn their old, evil self over to Christ, that the process of purification within a new believer might begin. We cannot do this of our own will. We need the Holy Spirit to indwell us.
Don’t be fooled by outward appearance. It is what is in the heart that matters. Be sure your heart belongs to Christ.