The sermon exposes the danger of legalism by analyzing Jesus' confrontation with the Pharisees in Matthew 15, demonstrating how man-made rules replace genuine devotion. It argues that legalism produces heartless worship, where outward rituals mask a distant and unengaged soul, contrasting this with God's desire for inner transformation and sincere love. The preacher warns against both Roman Catholic sacramentalism and evangelical will-worship, asserting that neither approach honors God when it relies on human invention rather than divine command. True worship requires a renewed heart aligned with the truth of Scripture, rejecting any practices not explicitly ordained by God. Believers are urged to examine their own hearts and commit to worshipping God exclusively in the manner He has revealed.