Roman law allowed for a freeman to intercede on behalf of a slave.
While a fugitive in Rome, Onesimus met Paul and was converted by him (Phile. 10). It is possible that Paul had also converted Philemon (Phile. 19).
Since Paul knew Philemon, he could intercede on Onesimus’ behalf. Having seen the change wrought in Onesimus, Paul was willing to do so. (One had to be a Roman Citizen to do this). Did Paul “flaunt” his Roman citizenship? Example: Acts 16:37, 38; 22:25-29
Application For Us
Like Onesimus, we needed someone to intercede on our behalf (1 John 2:1; 1 Tim. 2:5). We needed someone who knows our Master and is in good standing with Him (Mt. 17:5). We needed someone sympathetic to our plight (Heb. 4:15).