Ephesians 3 (New International Version)
Paul the Preacher to the Gentiles
1For this reason I, Paul, the prisoner of Christ Jesus for the sake of you Gentiles—
2Surely you have heard about the administration of God's grace that was given to me for you,
3that is, the mystery made known to me by revelation, as I have already written briefly.
4In reading this, then, you will be able to understand my insight into the mystery of Christ,
5which was not made known to men in other generations as it has now been revealed by the Spirit to God's holy apostles and prophets.
6This mystery is that through the gospel the Gentiles are heirs together with Israel, members together of one body, and sharers together in the promise in Christ Jesus.
7I became a servant of this gospel by the gift of God's grace given me through the working of his power.
8Although I am less than the least of all God's people, this grace was given me: to preach to the Gentiles the unsearchable riches of Christ,
9and to make plain to everyone the administration of this mystery, which for ages past was kept hidden in God, who created all things.
10His intent was that now, through the church, the manifold wisdom of God should be made known to the rulers and authorities in the heavenly realms,
11according to his eternal purpose which he accomplished in Christ Jesus our Lord.
12In him and through faith in him we may approach God with freedom and confidence.
Verse3: by revelation is the mystery made know; not by reason
Verse5: this mystery is not revealed to Paul only, but all the holy apostles and prophets BY THE SPIRIT.
Verse 6: the mystery is the revelation that salvation is unto ALL humanity who believe. We are now fellow heirs, and partakers of the promises that were unto the chosen people of God, in Christ, because of the gospel; that is the miracle of his death in our stead, his burial, and his ressurection. (1 Corinthians 15:3-4)
One cannot understand the mystery without the Spirit. The Spirit is promised as a gift to all who believe. John 7:38,39 - He who believes in me as the scripture has said, rivers of living water will flow from within him. By this he meant the Spirit, whom those who believed in him would later receive.
verse 10: God intends for the body of Christ to be the testimony of his wisdom. He is using us to prove to the world the wisdom of his plan opposed to the wisdom of the world. God's wisdom will make the wise of this world ashamed. The church, God's body, defies the wisdom of man
1 Timothy 3:16And without controversy great is the mystery of godliness: God was manifest in the flesh, justified in the Spirit, seen of angels, preached unto the Gentiles, believed on in the world, received up into glory.