God reveals his truth to Paul. Paul calls it a mystery. God gives it to Paul so he can share it with the church in Ephesus; he’s not supposed to keep it to himself.
This isn’t something Paul figures out on his own; he doesn’t logically deduce it or make it up. This isn’t something someone else teaches him, and he doesn’t read about it in the Bible. (Remember that the New Testament doesn’t exist in Paul’s time: He and the other church leaders are still writing it, and it’s quite a bit later before someone compiles it to form the New Testament.)
So how does Paul discover this mystery of God? He learns it directly from God.
First Jesus appears to him as Paul travels to Damascus to hunt down Christians. A bright light flashes, Paul falls to the ground, and God speaks. He gets Paul’s attention. God tells Paul to wait for further instructions (Acts 9:3-6).
But God doesn’t tell Paul everything he needs to know about God and his mystery. This is just the beginning, the first step. Throughout Paul’s life, God continues to reveal more and more to Paul, explaining more fully the mystery of God’s grace to us. Paul spends his life learning how to follow God, telling people about him, and writing to others so that they – and we – may know this marvelous mystery of God’s grace and how he can change our lives, just as he did to Paul.
How does God reveal himself to you? How does his Holy Spirit teach and guide you?