G.W. North emphasizes the significance of the blood of Jesus as the ultimate cleansing agent for sin, contrasting it with the Old Testament sacrifices. He explains that while the blood of bulls and goats provided temporary atonement, the blood of the Lamb offers permanent redemption and sanctification, cleansing us from both known and unknown sins. North highlights the importance of walking in the light to experience continuous cleansing and the distinction between sins of ignorance and known sins. He asserts that true believers, while acknowledging their imperfections, are empowered by the blood of Christ to live in fellowship with God without habitual sin. Ultimately, the sermon reveals the profound mystery of redemption through the blood of Jesus, which is effective for all sin, past and present.