The central message of this sermon is that marriage, as ordained by God, is a sacred and fundamental relationship that has been severely impacted by sin. The speaker argues that Jesus' design for marriage elevates it beyond being just a human agreement or contract to a divine institution, where what God has joined together should not be separated. Furthermore, Christ's words and work deepen the commitment in marriage, making it not just about outward actions but also about the inward heart. The speaker emphasizes that sin introduces duplicity in human nature, causing us to hide our true selves, and this is particularly evident in the marriage relationship. Ultimately, the sermon highlights the importance of understanding God's original design for marriage and recognizing Christ's role in redeeming it, allowing believers to live in harmony with His plan.