Ephesians 3:1: The Apostle Paul was a willing bond slave to Christ Jesus (Romans 1:1). He was enslaved to serve the Gentiles (Acts 26:17).
Ephesians 3:2: Paul was given a Body of Truth specifically for us (Colossians 1:24-26).
Ephesians 3:3 and 4: God has secrets (Deuteronomy 29:29). His secrets remain secrets until they are revealed (Ephesians 1:9). God revealed His secrets to us through Paul alone (Acts 26:16).