For whose sake was Paul a prisoner of Jesus Christ?

Les explains that in Ephesians 3:1 Paul calls himself the prisoner of Jesus Christ, and the purpose is stated plainly: "for you Gentiles." Les notes that Paul was not only a bondslave of Christ but also a literal prisoner of Christ for this distinct purpose. This was part of God's plan to bring pagan Gentiles out of their sin and spiritual darkness into the knowledge of the gospel. Les then goes back to Acts chapter 9 to show how this began, reminding listeners that Paul had been a religious zealot who honestly thought he was serving the God of Abraham by stamping out anything that referred to Jesus of Nazareth in Israel. But God stopped him on the road to Damascus, and his salvation took place there. While Saul was still making his way into town, blind, the Lord spoke to Ananias and told him to go to the street called Straight and inquire at the house of Judas for Saul of Tarsus, who was praying. Ananias was to understand that Saul was being made ready for something special.