In that case it would lose all value before the eyes of God, for "God loves a cheerful giver" (2 Cor 9:7). Therefore I sent Onesimus to you.
If you decide to make him my servant, then you will do this by your good will. The Apostle does not insist that Onesimus be sent back to him, because there was no extreme need for this.
There were always many persons around him ready to do everything necessary for him. He leaves this to Philemon's freedom.
St. Chrysostom says: "By these words the Apostle suggests that he had Philemon in view more than the slave, because he shows him great respect: 'without your consent,' he says, 'I would do nothing.'"
"And by this he softens Philemon" (Theophylact). A man is especially inclined to a request when the matter itself is beneficial and is arranged according to his will.
Then there are two goods: the giver receives benefit, and the receiver is in greater security. He did not say, "not by compulsion," but, "not as though by compulsion."
Although I knew, he says, that if you had not been informed about this matter and had learned of it unexpectedly, you would not have been angry.
Nevertheless I acted with special caution, "that your good deed might not be as though by compulsion." Let us complete this with Theodoret's words: "I want you also to acquire benefit from this, and by your own consent to draw profit."