Romans 13:8

From the Believer's Bible Commentary, by William MacDonald.

"The one debt that is always outstanding is the obligation to love.  The word used for love in Romans, with only one exception (12:10) is agape, which signifies a deep, unselfish, superhuman affection which one person has for another.  This otherworldly love is not activated by any virtue in the person loved; rather, it is completely undeserved.  It is unlike any other love in that it goes out not only to the lovable but to one's enemies as well.

"This love manifests itself in giving, and generally in sacrificial giving.  Thus, God so loved the world that He gave His only begotten Son.  Christ loved the church and gave Himself for it.

"It is primarily a matter of the will rather than the emotions.  The fact that we are commanded to love indicates that it is something we can choose to do.  If it were an uncontrollable emotion that swept over us at unexpected moments, we could scarcely be held accountable.  This does not deny, however, that the emotions can be involved.

"It is impossible for an unconverted person to manifest this divine love.  In fact, it is impossible even for a believer to demonstrate it in his own strength.  It can only be exhibited by the power of the indwelling Holy Spirit.

"Love found its perfect expression on earth in the Person of the Lord Jesus Christ.

"Our love to God manifests itself in obedience to His commandments.

(emphases in original)