I came across this gem today in my reading of St. Gregory the Great’s Pastoral Care (ACC Series):
If, then, the fear of punishment goes on restraining a man from evil-doing, surely, no liberty of spirit pervades the soul so dominated by fear. For if it did not fear the punishment, it would doubtless do evil. The mind, therefore, that is under the slavery of fear, does not know the grace of liberty. Good should be loved for its own sake, not pursued under the compulsion of established penalties. The man who acts well from fear of the evil of torments, wishes that what he fears did not exist, so that he might boldly commit sin. Wherefore, it is clearer than daylight that innocence is thus lost before God, for in His eyes sin of desire is present.
This is a really fancy way of saying that outward obedience is not enough. Obedience to the Law out of compulsion or fear of punishment is not the same as “serving in the new way of the Spirit” (Romans 7:6). Covetous desire (concupiscence) is as sinful as the outward act, which is the point of Jesus’ words in the Sermon on the Mount. That is why no one can hope to be justified by merely observing the letter of the Law. For one may, by sheer force of will, avoid outward crimes and sins, and yet become guilty by the fact that he desires the evil.
“Good should be loved for its own sake,” not simply because of earthly reward or punishment. Try instilling this into your children! (Or yourself!) This statement alone was all I needed to cry out to the Lord in repentance. “Wretched man that I am, who will rescue me from this body of death? Thanks be to God, through Jesus Christ our Lord!”