1.2 Love is expressed in action and in feeling. As to love in action, I believe men have been given a law, a settled commandment. (Dt 5:6) But what need has love of commandment? You are commanded to show love in action so that you may have merit; the sensation of love is its own reward. We do not deny that this present life can, by divine grace, give experience of its beginning, and of the progress, but we stoutly maintain that is is fully known only in the happiness of the life to come. How then were things which could not in any way be fulfilled made commandments? Or, if you would rather say that it is the sensation of love which is commanded, I do not disagree, so long as you agree with me that it can never and never will be possible for any man to fulfil it. For full dares to claim for himself what even Paul owned he did not understand (Phil 3:13)? The Lawgiver knew that the burden of law was greater than men could bear, but he judged it to be useful for this very reason to advise men that they were not able to fulfil it, so that they might know clearly what end of righteousness they ought to strive as far as their powers permit. So by commanding what was impossible he made men, not prevaricators, but humble, so that every mouth may be silent and all the world made subject to God, for no one will be justified in his sight by keeping the law (Rom 3:19-20). So accepting that command and aware of our own insufficiency, we shall cry to heaven and God will have mercy on us (1 Mc 4:10). And we shall know on that day that God has saved us not by the just works we have done, but because he is merciful (Ti 3:15).
This is what I should say if we were agreed that the sensation of love is commanded by law. What it seems to us is love in action much better, for when the Lord said, "Love your enemies" he spoke immediately afterward of actions, "Do good to those who hate you" (Lk 6:27) [Sermon 50]