New Defender's Study Bible Notes
10 my son Onesimus. Paul called Onesimus “my son” because he had led him to Christ, just as he had Timothy (II Timothy 1:2), Titus (Titus 1:4), and even Philemon (Philemon 19). Before that, Onesimus had been one of Philemon’s servants (actually “bondservant” or “slave”), and had run away, apparently stealing from his master as he did (Philemon 18). As a born-again Christian now, however, Onesimus wished to return to his master and make amends, and Paul encouraged him. Every new Christian, to the extent it is possible, should similarly seek to redress any wrongs of which he had been guilty before his conversion.