Ephesians 3:3,4 - Made known to me by revelation

3:3

Paul here is referring to the Damascus road conversion. Paul was on his way to persecute more Christians, but Jesus grabbed a hold of him and changed the whole direction and purpose of his life. Paul would now be Christ’s apostle to the Gentiles. In Galatians Paul makes clear that he received the gospel directly from Christ, he did not receive it second-hand.  

3:4

The direction of Paul’s life did not make it obvious from a human perspective that he would be the apostle to the Gentiles. He was a most Jewish Jew, he was zealous for the Law and had been trained in the Law. He was an ardent opponent of Christ and the gospel, he loved persecuting the church. So Paul knew both from experience and learning how God’s plans were fulfilled in Christ. He now understood that the Old Testament was all pointing towards Christ, and he had personally experienced how the grace of God worked.