This short one-chapter book is a personal letter addressed to Philemon, whose slave, Onesimus, had run away, but whom Paul led to Christ. Now Paul was making a way to send him back to Philemon. The main exhortation for Philemon (and us) is to forgive others in Christ!
Here’s an outline of Philemon:
I. Prayer of thanksgiving for Philemon (1:1-7)
II. Petition of Paul for Onesimus (1:8-18)
III. Promise of Paul to Philemon (1:19-21)
IV. Personal matters (1:22-25)