The sermon emphasizes the importance of allowing Scripture to interpret Scripture as the infallible rule for understanding the Bible, rather than relying on external sources like tradition or reason. It explores this principle through examining how the New Testament authors utilize the Old Testament, highlighting the concepts of promise, principle, and pattern, and encouraging readers to actively engage with the text through prayer, cross-referencing, and recognizing the transformative power of God's word in their lives, ultimately leading to a deeper understanding and faithful application of biblical teachings.