Someone has said that this Epistle to Philemon is the finest specimen of early private Christian correspondence extant. We should expect this, since it was given by divine inspiration. And yet it all has to do with a thieving runaway slave named Onesimus, who was about to return to his former master.
The history behind the letter, which is deduced from a careful study of the Epistle itself, seems to be this: In the city of Colosse dwelt a wealthy Christian man by the name of Philemon, possibly the head of a large household, and like many in that day, he had a number of slaves or bondsmen. Christianity did not immediately overturn the evil custom of slavery, although eventually it was the means of practically driving it out of the whole civilized world. It began by regulating the relation of master and slave, thus bringing untold blessing to those in bondage.
This man Philemon evidently was converted through the ministry of the apostle Paul. Where they met, we are not told; certainly not in the city of Colosse, because in writing the letter to the Colossians, Paul makes it clear that he had never seen the faces of those who formed the Colossian church. You will recall that he labored at Ephesus for a long period. The fame of his preaching and teaching was spread abroad, and we read that "all... in Asia heard the word." Among those who thus heard the Gospel message may have been this man Philemon of Colosse, and so he was brought to know Christ.