How does Jesus define true uncleanness in this passage?

In Matthew 15, Jesus redefines what constitutes true uncleanness, asserting that it arises from within a person's heart rather than from external influences (Matthew 15:18). He indicates that evil thoughts, such as murders, adulteries, and other sins, emanate from the heart and serve as the source of a person's defilement. This radical teaching confronts the prevailing understanding of the Pharisees, who placed significant emphasis on dietary laws and ritual purity, suggesting that true holiness is not achieved through external compliance but by addressing the internal condition of the heart.

This redirection toward the heart's nature emphasizes the need for a spiritual renewal rather than mere behavioral modification. Jesus teaches that the heart is deceitful and wicked (Jeremiah 17:9), highlighting the importance of divine intervention in transforming a person's nature. By understanding that real uncleanness comes from within, believers are led to seek a savior who can cleanse and renew them, reaffirming the necessity of faith in Christ for true purity.