4 In reading this, then, you will be able to understand my insight into the mystery of Christ.
In vs 4, Paul states that as they continue on in the letter they will fully understand his insight into the mystery of Christ. Paul says that Jesus is the author of this mystery. Paul may have been the messenger but the message is from the Lord Jesus Christ Himself. Remember Jesus is full of grace and truth. Paul says that divine illumination will come as they read about this because the Holy Spirit will reveal it to them. We cannot understand divine truth unless the Holy Spirit is part of the equation. He takes that what He hears and passes it unto us. You will never understand the things of God apart from the Holy Spirit. He is the divine revealer. Paul says keep reading there is more to come.