“Meanwhile praying also for us, that God would open to us a door for the word, to speak the mystery of Christ, for which I am also in chains.”
“for which I am also in chains”
It was the preaching of the mystery that put Paul in jail in the first place. The gospel compelled Paul to preach. He felt a burden of “woe” if he did not (1 Cor. 9:16; cf. Acts 4:20).
Paul was not only in jail, but he was in chains. It is easy to preach the gospel when the circumstances are comfortable. Comfort did not affect whether Paul preached or not. Paul sits in chains and asks the Colossians to pray that God would allow him to preach even in adverse circumstances. Paul saw a potential convert in every human being. We just see people, antagonistic people, weak people, negative people. All Paul saw was souls for whom Christ died.
Paul often spoke of his imprisonment (Phil. 1:7, 13-14, 16; Col. 4:18; Phile. 1, 9-10,13). The gospel is why Paul is sitting in jail. He took a negative circumstance and turned it into a blessing. While sitting in prison in Rome, he writes epistles with which the Holy Spirit blessed Christians for 2000 years.
Paul always took his negative circumstances and turned them into blessings.