Paul begins, For this cause I, Paul, am the prisoner of Christ Jesus on behalf of you Gentiles. He explains the special task God gave him. By revelation the mystery was made known to me. In earlier ages it was kept hidden, but now the Spirit has revealed it to the apostles and prophets. The mystery is this: the Gentiles are fellow heirs and fellow members of the body, and fellow partakers of his promise in Christ Jesus through the Good News.
Paul does not think he deserves this task. To me, the very least of all saints, was this grace given, to preach to the Gentiles the unsearchable riches of Christ. God's plan was hidden for ages, but now through the assembly the manifold wisdom of God might be made known to the principalities and the powers in the heavenly places. Manifold means having many sides, like a jewel. Because of Christ, In him we have boldness and access in confidence through our faith in him. So Paul asks them not to lose heart because of his troubles.
Paul then writes one of the great prayers of the Bible. I bow my knees to the Father of our Lord Jesus Christ. He asks God to make them strong inside by His Spirit, that Christ may dwell in their hearts through faith. He prays that, being rooted and grounded in love, they may comprehend the width and length and height and depth, and to know Christ's love which surpasses knowledge. The chapter closes with praise: Now to him who is able to do exceedingly abundantly above all that we ask or think, according to the power that works in us, to him be the glory.