What is the mystery that Paul speaks about?
The mystery is the revelation of secrets held in the mind of God but now revealed—specifically God's righteousness manifested without the law. This truth belongs to a different economy after God turned to the Gentiles, not the Old Testament law economy. It is not found in the Gospels or Old Testament in the same language.
Les explains that this mystery is tied to the righteousness of God being manifested without the law, witnessed by the law and the prophets. He emphasizes Pauline teaching but insists the Old Testament is not to be forgotten, since it all dovetails together. The Old Testament operated under the economy of law for Israel—temple worship, priesthood, and sacrifices—but when God turned to the Gentile, that economy slipped off the scene and something totally different came in. Les says this language is not found in the Gospels or Old Testament; it is part of the revelation Paul speaks of, the mystery and secrets held in the mind of God but now being revealed.