David Wilkerson emphasizes the relevance of the Old Testament for modern believers, arguing that it provides essential context and understanding for the New Testament. He illustrates how the stories and events in the Old Testament serve as types and shadows of spiritual truths, such as Israel's journey symbolizing the Christian walk and the tabernacle representing heavenly realities. Wilkerson encourages believers to study these examples to avoid the pitfalls of unbelief and disobedience that Israel faced. He highlights specific stories, like the fall of Jericho and Jacob's wrestling with God, as practical lessons for overcoming spiritual challenges today. Ultimately, he calls for a diligent engagement with the Old Testament to enrich one's faith and understanding.