What does Matthew 15:17 mean?

The law of Moses labeled many edible things as unclean. Consuming those things made the person ceremonially unclean, as well, requiring specific actions be declared "clean" again. The Pharisees' traditions included a series of strict rules meant to prevent even unknowingly contacting these unclean items. Thus, they required a hand-washing ritual before eating (Matthew 15:1–2). According to their interpretation, if someone unknowingly touched something unclean, washing your hands according to specific guidelines would keep you from accidentally eating that bit of uncleanness.

Jesus has completely rejected that idea, saying it's not what goes into the mouth that defiles a person; it's what comes out of the mouth that does that (Matthew 15:11). The disciples asked Jesus to explain this; Peter suggested Jesus was speaking in a parable (Matthew 15:15). Perhaps they were wondering about all the dietary restrictions that were included in the Law.

Jesus asks them to understand that what a person eats—the physical substance itself—simply travels through the body and out the other side. His point is that this is merely a physical process. The morsel of food, all by itself, doesn't touch the spirit or soul of a person. It can't cause a person to become sinful.

This explanation is not meant to dismiss the dietary requirements of the law of Moses (Matthew 5:17–19). Jesus kept those laws perfectly. He obeyed all the commands, and He did so according to both their letter and their intent (Matthew 12:1–8). Those restrictions were about the heart of Israel in submission to God, keeping Israel set apart for God as a holy people. The point Jesus makes here is like those presented in His Sermon on the Mount (Matthew 5:1–2). The material, physical contents of those restricted foods were not the danger, in and of themselves. They were just food. Unknowingly swallowing something unclean did not add to a person's sinfulness. The food itself was not the issue, it was whether a person sought to obey God's command. That is is why ritual handwashing did not keep anyone from sinning.

In other words, those who knowingly ate unclean foods did become ceremonially unclean; that uncleanliness was due to their actions and intentions, not mere contact with a physical object.