"Love: this is the decisive word... Without this 'love' everything disintegrates and is unacceptable; in this love everything is integrated, united, and pleasing to God. What is this love?
...we must exclude any definitions that seek to understand the essence of love as human behavior, as disposition, dedication, sacrifice, will for community, as feeling, passion, service, or deed. All this without exception can exist without 'love'... Everything we usually call love, everything that dwells in the farthest depths of the soul and in visible deeds, indeed, even brotherly or sisterly service to the neighbor that springs from the pious heart--all this can lack 'love.'
So, if there is no conceivable human behavior that would as such unambiguously qualify as 'love'... then this poses an enigma, an open question as to what else the Bible could still mean by 'love'.
The answer is: God is love. For the sake of clarity, this sentence must first be read with the emphasis on the word God, even though we have become accustomed to emphasize the word 'love'. God is love: that is, love is not a human behavior, sentiment, or deed, but it is God who is love. What love is can be known only by one who knows God; the reverse is not true...
Thus, nobody knows what love is except through God's self-revelation. Love is therefore God's self-revelation. God's revelation, however, is Jesus Christ... Christ is the sole definition of love.
Love is not what Christ does and suffers, but what Christ does and suffers. Love is always Jesus Christ himself. Love is always God himself. Love is always God's revelation in Jesus Christ.
However... only the concrete doing and suffering of this human being Jesus Christ will make clear what love is... To the question, 'In what does love consist?' we continue therefore to answer with scripture: the reconciliation of human beings with God in Jesus Christ."