"Don’t you see that whatever enters the mouth goes into the stomach and then out of the body?"Jesus is explaining that food can be physically “clean” or “unclean,” but it doesn’t affect the “cleanliness” of 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.
"For out of the heart come evil thoughts, murder, adultery, sexual immorality, theft, false testimony, slander."Jesus is clarifying the nature of evil - and the person within. Here we find clarity about the source and nature of evil. Evil does not arise from a horned guy with a pitchfork from a fiery dungeon. Evil comes from self-centeredness. Evil comes from greed and the desire to dominate others and consume the things of the physical world. Evil comes from the notion that the world revolves around us and the things around us are intended for our enjoyment.
These are being characterized by Jesus as being unclean because they relate to the character of the person within. If the person within - the spirit-person - wants to reject the Supreme Being and search for happiness within self-centered desires, this is being defined as being unclean.
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)
(For a translation of Jesus' statements from the Gospel of Matthew without institutional sectarian influence, see the Devotional Translation - translated from the original Greek texts.)