What does Ephesians 3:1 mean?

Chapter 3 begins by speaking of the mystery of Christ revealed (Ephesians 3:1–13). The second part of this chapter is Paul's prayer for spiritual strength, which closes the first half of his letter (Ephesians 3:14–21). He begins this passage by reminding his readers of his status as an imprisoned man. He was under house arrest in Rome at this time. In addition, it was on behalf of his ministry to Gentiles that he had been arrested in the first place. This occurred in Jerusalem when Paul was arrested by Jews who thought he had taken a Gentile into an inappropriate area of the temple (Acts 21:7—22:29).

From that moment forward, Paul would spend a total of four to five years in custody, between jail and transit to house arrest in Rome. His life was marked by suffering and persecution, making him a "prisoner for Christ Jesus." Yet even while chained, Paul used his time to communicate the gospel and write letters to churches, such as this letter that communicated the mystery of Christ.