For this reason I, Paul, a prisoner of Christ Jesus on behalf of you Gentiles—(Eph. 3:1)
I therefore, a prisoner for the Lord, urge you to walk in a manner worthy of the calling to which you have been called (Eph. 4:1)
Paul’s discussion on his stewardship of the mystery of the Gospel is so significant that he must interrupt his intention to tie the walk of the believer to Christ’s work in salvation; (e.g., “walk” in 2:10; 4:1, 17; 5:2, 8, 15). The phrase in 4:1, “I… a prisoner of the Lord,” carried over from 3:1, “I… a prisoner of Christ Jesus,” indicates that 4:2-6:24 originally would have followed 2:22. The flow still works if you skip 3:1-21.
However, by inserting the discussion of 3:2-31, the walk of the believer now relates to the revelation of the equal spiritual footing of Jewish and Gentile believers in Christ (3:6). It also means Paul intends for the believer to be empowered by the prayer and truth of 3:14-21: We must know the love of Christ deeply and increasingly in order to accomplish the life of the believer (4:1-6:9), and we must know the love of Christ deeply and increasingly in order to to stand in the warfare being waged from the heavenlies (6:10).