“Are you still so dull? Don’t you see that whatever enters the mouth ...’” (Matt. 15:16-20)

Peter said, “Explain the parable to us.” “Are you still so dull?” Jesus asked them. “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.” (Matt. 15:15-20)

What does being defiled have to do with being clean?

Jesus is further explaining the meaning behind his point about being clean or unclean ("defiled"). His original statement about this was related to washing the hands.

Jesus is explaining that food can be physically “clean” or “defiled,” but it doesn’t affect the person within. This is because the person is not the physical body. This is what Jesus was trying to teach them: That we are not the physical body.

We are the spirit-person within these physical bodies. The cleanliness of this person within is reflected by their words and activities. Words and activities revolving around our self-centeredness, and our assumption that the universe revolves around us reflect the condition of our inner person.

What does 'out of the heart' mean?

Jesus is clarifying the nature of our consciousness - coming from the person within combined with the use of the mind. Here we find clarity about the source and nature of consciousness.

Evil does not arise from a horned guy with a pitchfork from a fiery dungeon. Evil arises from a consciousness of self-centeredness.

These are being characterized by Jesus as being defiled because they relate to the character of the person within. If the person within - the spirit-person - wants to search for happiness within self-centered desires, this is being defined as being defiled.

This means that being clean, on the other hand, relates to the person within living within the potential of our innate identity: Our understanding that we were created by the Supreme Being and we are ultimately His loving servants and children. This is why Jesus' most important instruction was:
" 'Love the Lord your God with all your heart and with all your soul and with all your mind.' This is the first and greatest commandment." (Matt. 22:37-38)