Why are some of Paul's letters called the prison epistles?
Paul wrote Ephesians, Philippians, Colossians, and Philemon from Rome while under house arrest. Because he was literally in prison during their writing—though confined by house arrest rather than a dungeon—these four letters are commonly called the prison epistles.
Les explains that Paul wrote Ephesians, Philippians, Colossians, and Philemon from Rome while in prison under house arrest. The next year, while he was still in Rome and still under house arrest, that is why they are called the prison epistles. He was literally in prison, but it was not a dungeon; it was a house arrest.