This letter is unique in the New Testament as a letter to a friend and convert about some family matters. It has the smell of the New Testament – full of love and grace and is one brother writing to another brother about a third brother!
The issue is Onesimus, who was Philemon’s slave – an unsatisfactory servant, v.11 – who had likely stolen from Philemon, v.18 and then run away. He eventually finds Paul and more importantly Christ, and is changed. Part of repentance is cleaning up messes, so Paul wants to send Onesimus back to his master Philemon. In verse 16 we find the heart of the letter – treat him no longer as a slave. Paul’s appeal is for forgiveness and freedom.
Paul has written before that slaves should seek freedom if they can, but not be too anxious about it; that masters should free slaves if they can. Paul appeals to Philemon to show mercy and grace to Onesimus who is deserving, in the world’s eyes, of death.
Slavery may be illegal now, but tyranny continues and will likely do so until Christ returns. We are called, like Philemon, to be different – loving, forgiving and freeing.