8 To me, who am less than the least of all the saints, this grace was given, that I should preach among the Gentiles the unsearchable riches of Christ, 9 and to make all see what is the fellowship[a] of the mystery, which from the beginning of the ages has been hidden in God who created all things through Jesus Christ;[b] 10 to the intent that now the manifold wisdom of God might be made known by the church to the principalities and powers in the heavenly places, 11 according to the eternal purpose which He accomplished in Christ Jesus our Lord, 12 in whom we have boldness and access with confidence through faith in Him. 13 Therefore I ask that you do not lose heart at my tribulations for you, which is your glory. Ephesians 3:8-13
The mystery that has been hidden that now has been made known is salvation is found in Jesus Christ the Son of God. Under the Old Covenant the nation of Israel lived under the law of God. The purpose of the law was to reveal to man’s his need of a savior. The law of God is the righteousness of God revealed and it is impossible to perfectly keep the law of God. This is why under the Old Covenant that the Lord established animal sacrifices to cover over the sins of the people. These sacrifices had to be performed on a daily basis because they didn’t remove sin, but simply covered it.
But under Christ our sins are forgiven and removed. Under Christ we are righteous through faith in Jesus Christ. Our righteousness is not based upon our performance. Because of Jesus we are able to go boldly before the throne of grace.
The apostle Paul was given the charge by the grace of God to preach the gospel. The apostle Paul was chosen for this and it was by the grace and mercy of God alone. No one ever picks their calling or anointing in God’s kingdom. It is chosen for us and as we walk with God we are refined and transformed into the person He has called us to be.