Augustine of Hippo

The grace of God, by which our sins are forgiven, is the condition of our being reconciled to Him, whereas peace is that wherein we are reconciled.

And addressing himself to Philemon, Paul says: “that your kindness may not be as it were of necessity, but voluntary.” … Now wherever there is the express statement not to do this or that, and whenever the performance of the will is required to do or refrain from some action, in keeping with God’s commandments, that is sufficient proof of the free choice of the will. Let no one, therefore, blame God in his heart whenever he sins, but let him impute the sin to himself.

But when you have joy of a man in God, it is God rather than man that you enjoy. For you enjoy Him by whom you are made happy, and you rejoice to have come to Him in whose presence you place your hope of joy. And accordingly, Paul says to Philemon, “Yea, brother, let me have joy of thee in the Lord.” For if he had not added “in the Lord,” but had only said, “Let me have joy of thee,” he would have implied that he fixed his hope of happiness upon him, although even in the immediate context to “enjoy” is used in the sense of to “use with delight.” (On Christian Doctrine 1.33)