In this sermon, the preacher emphasizes the seriousness of sin by contrasting it with righteousness. He explains that to truly understand the sinfulness of our own lives, we must look to Christ and see His righteousness and purity. The preacher highlights that sin is lawlessness against God and originated with Satan. He also discusses how sin relates to Christ, ourselves, and Satan, emphasizing the continuous nature of sin. Overall, the sermon aims to help listeners grasp the gravity of sin and the need for Christ's redemption.