The central message of this sermon is that the Bible has a rich structure and organization that underlies its meaning and significance. The teacher explains how the concept of covenant is essential to understanding the difference between the Old Testament (outside-in) and New Testament (inside-out), with the new covenant being sealed in the blood of Jesus Christ. This new covenant is the foundation of the Christian life, and it is based on faith in Christ rather than human effort or adherence to rules. The teacher also highlights how different arrangements of the Old Testament books can reveal various themes and theological perspectives. Ultimately, the sermon aims to help listeners understand the deeper significance of the Bible's structure and organization, which will enable them to gain a richer understanding of God's Word and their relationship with Him.