Philemon 1:9, commentary and pictures

Paul deliberately set aside his right and authority to command what was Philemon's duty as a Christian, choosing instead the language of entreaty for love's sake. He would not urge by command but would beseech, appealing on the ground of love rather than simply asserting authority. He grounded that entreaty in his personal standing, describing himself as an aged man and now also a prisoner of Jesus Christ. The force of the appeal drew upon his age and his present imprisonment for Christ.

The entreaty was made on behalf of Onesimus, his repentant convert, whom he asked Philemon to receive. His title as prisoner of Jesus Christ was literal on his way to Rome, where he was fettered and stigmatized and bound by a chain with no release. He arrived in circumstances different from what he had hoped for in proclaiming the gospel, yet his sufferings only endeared him the more to the Christians in Italy. They had eagerly looked forward to his visit since his letter to the Romans, and came out to meet and welcome him.

The description of the aged prisoner fits Paul in chains preaching Christ in the stronghold of the Caesars, as one of the few and despised bearers of God's truth. The same description fits Paul writing from his prison in Rome to set before his fellow believers the unsearchable riches of Christ, the treasure of grace freely offered to fallen humanity. From that prison-house at Rome he wrote to the brethren in Ephesus about those riches. It was a theme that human language is inadequate to express in its fullness.