The Romans did not deny their slaves all hope of freedom. The law provided for their manumission, or liberation, in various ways. Most commonly, the master took his slave before an official, in whose presence he turned the slave around and pronounced the longed-for words liber esto, “Be free,” and struck him with a rod.
Manumission could also be performed by various other means, such as writing a letter, making the slave guardian of one’s children, or placing on his head the pileus, or cap of liberty. Unless manumission was decreed by law rather than by a private owner, the slave was bound to remain a client to his master and to perform any obligations placed upon him at the time of manumission. In the Roman Empire, it was possible for freedmen to rise steadily to positions of influence and even of civic authority, but their property, when they died without heirs, reverted to their former masters. One such instance was that of Felix, procurator of Judea (Acts 24:25-27).
As we begin this short study of Philemon, keep these things we have just learned in mind. They will help give perspective as to why and how it is that Paul is writing this letter to his convert, Philemon on behalf of Onesimus, a slave that was also a convert of Paul’s for Christ.
The Bible In Your Hand 