How did God reveal truth progressively from the Old Testament to the New Testament?

Les teaches that all of Scripture, from Genesis to Revelation, is a progressive revelation. As we come up through the Old Testament, God is always revealing something that the fellows back there didn't know. Then in the New Testament, God begins to reveal things that weren't in the Old Testament. Especially through the Apostle Paul, God gives revelations that were never hinted in the Old Testament and that Jesus never spoke of. Within Paul's letters, particularly the seven Church letters, there is again a progressive revelation from the beginnings of his writings to the end, following the format of first doctrine, then reproof, then correction, and then instruction in righteousness. Les points this out to show how beautifully the Book is put together, noting Paul did not sit down planning to put doctrine first, reproof, correction, and instruction; Paul likely did not even realize he was writing Scripture.