Do not owe anyone anything, except to love one another, for the one who loves another has fulfilled the law.
Romans 13:8 CSB
All you need is love
Beatles
All you need is love, love, love is all you need.
These words are from a 1967 song by the Beatles, and they mirror what Paul says in this passage, although the Beatles likely had in mind a different kind of love than Paul. For most people in the world, love is an emotional feeling. But for Paul, and for Jesus (Matt. 22:37-40), love is more than just a feeling. Love seeks for the good of the one who is loved; it is active, an act of the will.
The Old Testament Law, as well as most laws today, are concerned with how we should be treating each other, making sure that we do not cause harm to each other. Mostly they tell us what we should not be doing. In contrast to that is Paul’s positive direction here, what we should do. And that is to love. If I am loving you, I will not be causing you harm, and thus I am accomplishing what the law, in its negative fashion, is trying to do.
Love here is expressed as a debt, the debt of love, the one debt I can never repay, but should always be making payments on. This debt is not the result of other people’s actions on my behalf. Rather it is because of what God did for me (1 John 4:11). Because he loved me, I must love others.