What does Matthew 15:20 mean?

Does unknowingly eating a bit of something "unclean" cause an Israelite to be defiled? The Pharisees said it did, so they washed their hands in a ritual manner before every meal to avoid it. Jesus said it does not; in fact, Jesus said nothing that goes into a person through the mouth can cause that person to be defiled. It's the sin in the human heart, revealed by the words that come out of a person's mouth, that defile a person (Matthew 15:11, 17–19).

Jesus provided a sample list of defiling sins in the previous verse (Matthew 15:19), though there are many more. Every single human carries defiling sin in his or her heart (Romans 3:1–11). Nobody is clean. The point of the Law of Moses was not to keep the people permanently clean from some external source of sin; the Law did not have the power to do that. Sin is something on the inside which our words and actions reveal. Jesus had come to earth to make it possible for the sin in us to be forgiven by God once and for all.

Christ concludes this discussion of the Pharisees by telling His disciples that eating with unwashed hands does not defile anyone. That's why He does not require them to participate in the ritual washing before meals. No tiny speck on an unclean thing, unknowingly and accidentally eaten, can ever touch their souls, which are already defiled with sin.

It's important to understand that Jesus is not commanding anyone not to wash their hands before meals. His point is only about what handwashing does not accomplish, spiritually. We know that consuming germs or other contaminants does have the ability to make us physically sick. It's a good idea for our physical health to wash before eating. It just won't do anything to make us more or less sinful or "defiled."