We find this little letter at the end of the series of letters in the New Testament to which Paul's name as a writer is attached. Precisely because it is the shortest of Paul's letters, it is placed at the back. It is a personal letter in which Paul makes a request to Philemon regarding a slave, Onesimus.
Paul wrote this letter with his own hand (see v. 19) along with Timothy while he was imprisoned in Rome in his "own rented dwelling" (AD 61-63; Acts 28). During that two-year period, Paul wrote a total of four letters. In addition to this letter to Philemon, also the letters to the Ephesians, Philippians and Colossians. From verse 22 we can more or less conclude that the letter was written at the end of Paul's imprisonment.
The letter is addressed to, among others, Philemon, Apfia and Archippus. The first two names only appear in this verse in the Bible. Philemon and Apphia may have been married to each other. We also read about Archippus in Colossians 4:17. From this we conclude that these three probably lived in Colossae (see also Col. 4:9 and 12 and Phm. 12 and 23).
a. vs. 1 and 2 Letter style and greeting.
B vs. 3 Mercy.
C. vs. 4-6 Paul's prayer for Philemon.
D vs. 7a Paul's joy in Philemon.
E. vs. 7b Refreshes the hearts / minds of the saints.
f. vs. 8 I might order (but don't use it).
G vs. 9 Paul, an old man.
H. vs. 10 and 11 Onesimus; useful, both for you and for me.
I vs. 12 Receive him as myself.
J vs. 13 Onesimus who serves on your behalf.
J vs. 14 What good you do.
H. vs. 15 and 16 A beloved brother; for you and for me.
I vs. 17 Receive him as myself.
G vs. 18 and 19a Paul, the debtor.
f. vs. 19b I don't say it (but I might).
D vs. 20a Paul's joy in Philemon.
E. vs. 20b Refresh my heart/mind.
C. vs. 21 and 22 Philemon's prayer for Paul.
a. vs. letter style.
B vs. 25 Mercy.
The purpose of the letter concerns Onesimus, a slave of Philemon who had apparently run away (cf. vs. 15 and 16). Without speculating too much, we may well conclude from this letter that Onesimus has been looking for peace for his heart. He was a useless slave (v. 11) who ran away too. Whether he was already looking for the Lord at that time, or whether this only came when he was on the run, we don't know. What is clear is that he ended up with Paul, all the way in Rome! He had to travel quite a distance for that.
And there in Rome he put his trust in the Lord. The latter is evident from Paul's words in verse 10 when he describes Onesimus as "my child whom I have begotten in my captivity" (cf. eg also 1 Tim. 1:2 and Tit. 1:3). Onesimus was "begotten" in Paul's captivity, that is to say: came to (re)birth. And now he was a "faithful and beloved brother" (Col. 4:9)!
Actually, Onesimus is a beautiful picture of how one can come to faith in this present time. By nature we are, as it were, useless, useless (cf. Rom. 3:12); at the same time we are slaves, namely: slaves of sin. But whoever seeks will find the Lord and share in the message precisely proclaimed by Paul in his captivity. In fact, we are now "begotten of Paul in his captivity" and are allowed to belong to the body of Christ, where He Himself is the Head of that same body! In the same way, we too may be "faithful and beloved" brothers (and sisters) by grace.
"... used to be useless (...) now very useful..." (v. 11).