The central message of the sermon is that true defilement originates not from external actions or ritualistic traditions, but from the heart—where evil thoughts, sins, and moral corruption reside. Drawing from Matthew 15:1–20, the pastor argues that Jesus confronts both legalism and antinomianism by exposing the Pharisees' hypocrisy in prioritizing human traditions over God's commandments, particularly the command to honor parents. Through a three-part dialogue with the Pharisees, the crowd, and the disciples, Jesus reveals that external practices like handwashing do not defile a person, but the heart's inner wickedness—manifested in murder, adultery, theft, slander, and deceit—does. The sermon emphasizes that the root of human sin is not in outward behavior but in the inward condition of the heart, which is inherently deceitful and incurable apart from divine intervention. The only solution, the preacher insists, is not self-effort, religious rule-keeping, or moralistic performance, but repentance and faith in Jesus Christ, who alone provides a new heart and eternal cleansing through His atoning sacrifice.