Onesimus - (Easton's Bible Dictionary)
Useful, a slave who, after robbing his master Philemon (q.v.) at Colosse, fled to Rome, where he was converted by the apostle Paul, who sent him back to his master with the epistle which bears his name. In it he beseeches Philemon to receive his slave as a "faithful and beloved brother." Paul offers to pay to Philemon anything his slave had taken, and to bear the wrong he had done him. He was accompanied on his return by Tychicus, the bearer of the Epistle to the Colossians (Philemon 1:16, 18).
The story of this fugitive Colossian slave is a remarkable evidence of the freedom of access to the prisoner which was granted to all, and "a beautiful illustration both of the character of St. Paul and the transfiguring power and righteous principles of the gospel."