Paul presents us with an interesting paradox. On the one hand, he says that we should owe no man anything that he can rightfully claim from us. But on the other hand, we must owe everyone more than we can hope to pay, that is, perfect love.
He extends and intensifies the concept of obligation. We must be more scrupulous within the limits of the common idea of indebtedness, and also infinitely widen the range within which it operates. Did not our failure to meet our obligations to God and man accrue for us an unpayable debt? Now that the debt has been paid, we are obliged not only to strive to avoid further indebtedness, but also to expand and perfect the giving of love.
This paradox is more apparent than real, because love is not an added duty but the inclusive framework within which all duties should be done. Love is the motivating power that frees and enables us to serve and sacrifice with largeness of heart and generosity of spirit.
If we view love as just the keeping of God's laws, we are stuck on a low-level, letter-of-the-law approach to righteousness. Do not misunderstand, keeping God's law is a necessary aspect of love, but love is far more complex. Commandment keeping is compulsory and can be done in an "only because" attitude, one that concludes, "I must love the person, but I don't have to like him." Drawing upon Christ's teaching, Paul gives an entirely new significance to the idea of obligation.