The verses in Matthew 15:18-20 in the King James Version of the Bible state:

18 But those things which proceed out of the mouth come forth from the heart, and they defile the man.

19 For out of the heart proceed evil thoughts, murders, adulteries, fornications, thefts, false witness, blasphemies:

20 These are the things which defile a man: but to eat with unwashen hands defileth not a man.

In these verses, Jesus is teaching his disciples about the importance of inner purity, as opposed to external rituals or traditions. He emphasizes that what truly defiles a person is not what goes into their mouth, but what comes out of their heart and mouth.

The context of these verses is a conversation between Jesus and the Pharisees and scribes. The Pharisees were critical of Jesus and his disciples for not adhering to the tradition of ceremonial hand washing before eating. This was considered a religious ritual for the Jews at the time, and the Pharisees were quick to point out their lack of adherence to this practice. However, Jesus takes the opportunity to teach them a deeper truth about the nature of sin and purity.

The theme of inner purity is central to these verses. Jesus emphasizes that true defilement comes from within a person, from the thoughts and intentions of the heart. The heart, in biblical terms, refers to the innermost depths of a person's being, including their thoughts, motives, and desires. Jesus lists several examples of evil thoughts and actions that come from the heart, such as murder, adultery, theft, and deceit. These examples serve to illustrate the depth of human sinfulness and the need for inner transformation.

The symbolism in these verses is powerful. Jesus uses the contrast between external and internal purity to make a profound spiritual point. The act of hand washing before a meal was a religious tradition meant to symbolize outward purity and holiness. However, Jesus teaches that this external ritual is of little significance compared to the condition of one's heart. The heart is the seat of a person's true moral and spiritual nature, and it is from the heart that both good and evil deeds flow. The symbolism here underscores the transformative power of an inner relationship with God, as opposed to mere adherence to outward religious practices.

These verses also point to the universal human condition of sin and the need for inner transformation. Jesus's teaching challenges the idea that external rituals or traditions can make a person truly pure or righteous. Instead, he emphasizes the necessity of a new heart and a right spirit, which only God can provide. This echoes the Old Testament prophecy in Ezekiel 36:26, where God promises to give his people a new heart and put a new spirit within them.

In conclusion, the verses in Matthew 15:18-20 offer a powerful and timeless lesson about the nature of true purity and defilement. They emphasize the need for inner transformation and spiritual renewal, rather than mere adherence to religious traditions or rituals. This teaching challenges us to examine our own hearts and attitudes, and to seek God's transformative work within us. It reminds us that true purity comes from a right relationship with God, which impacts every aspect of our lives, both inwardly and outwardly.