Matthew 15:16-20

Mat 15:16 (KJB)
And Jesus said, Are ye also yet without understanding?

The disciples had been walking with Jesus for well over two years now and Jesus turns to Peter and asks him if he is yet or still without understanding? They should have known the teaching skills and the symbols which Jesus used in teaching, especially in teaching by visible examples such as trees or plants. Understanding would come to the disciples more fully on the day of Pentecost.

Mat 15:17 (KJB)
Do not ye yet understand, that whatsoever entereth in at the mouth goeth into the belly, and is cast out into the draught?

Jesus then explains that when a person eats food, it goes into their mouth and then into their stomach and the waste matter goes into the latrine. This is a purely physical process and has nothing whatsoever to do with whether a person is defiled or not. In other words, He was asking the question as to how a physical process like eating and digestion or a ceremony can affect the spiritual condition of a person? It cannot affect a personís spiritual condition or else we would be able to eat our way into Heaven.

Mat 15:18 (KJB)
But those things which proceed out of the mouth come forth from the heart; and they defile the man.

It is not the food which goes into a man that defiles him but what comes out of the mouth. Jesus is making this a question of the stomach versus the heart. (Prov 4:23 KJV) Keep thy heart with all diligence; for out of it are the issues of life. When someone speaks evil of something, it is because they are evil or unsaved, and what they believe in the heart will be verbalized in the mouth and many times it is manifested in evil works. We saw how the evil people had rejected and hated the Lord Jesus Christ and the disciples when they began to teach and preach the Gospel. That hatred came out of a wicked heart and not out of eating certain foods. The external forms and ceremonies which were added to the law of God in the oral law only serve to puff up the flesh and make someone think more highly of themselves than they should be thinking. It is possible to keep all kinds of rituals and still be far from God. (Isa 29:13 KJV) Wherefore the Lord said, Forasmuch as this people draw near me with their mouth, and with their lips do honour me, but have removed their heart far from me, and their fear toward me is taught by the precept of men:

Mat 15:19 (KJB)
For out of the heart proceed evil thoughts, murders, adulteries, fornications, thefts, false witness, blasphemies:

Jesus goes beyond just evil thoughts and shows them how evil the heart of man really is. Man is so corrupted in his heart by sin that the range of sins goes from the evil thought right to the act of murder. Jesus gave some examples from the Ten Commandments. (Eccl 8:11 KJV) Because sentence against an evil work is not executed speedily, therefore the heart of the sons of men is fully set in them to do evil. (Jer 17:9 KJV) The heart is deceitful above all things, and desperately wicked: who can know it? Jesus is teaching the disciples how wicked the heart of man can be and why the necessity of the new birth. A person who has these types of sins in their hearts and the propensity to commit such sins, cannot be made righteous by means of a ceremony. This was the great error of the Pharisees. They emphasized the external facets of religion which could never take away an evil heart, all it could do was cover it up until it erupted again. Jesus wanted His disciples to know that sin is a matter of the heart and must be dealt with spiritually and not ritually.

Mat 15:20 (KJB)
These are the things which defile a man: but to eat with unwashen hands defileth not a man.

Those types of sins are what defiles a man but to eat with unwashen hands or neglect of any other ritual or ceremony does not defile the person. The heart is where the cleansing must be applied, not the hands by water. This is going to be the big dispute later on as the Christians butt heads with the Pharisees. The Pharisees will be pushing their ritual and ceremonies and the Christians will be stating that the heart must be cleansed by the blood of Christ. (Heb 10:4 KJV) For it is not possible that the blood of bulls and of goats should take away sins. It is the age old battle, the external visible ritual of religion versus the inward cleansing by the Holy Spirit in salvation through Christ. The blood of animals could never take away sins and always leaves the one who offers them dead in their sins. The blood of Christ removes the sins from a person and changes them from being spiritually dead to spiritually alive in Christ. (1 Cor 15:22 KJV) For as in Adam all die, even so in Christ shall all be made alive.