“‘To love him with all your heart, with all your understanding, with all your strength, and to love your neighbor as yourself’ is worth more than all burnt offerings and sacrifices.” (Mk 12:33)
From St Francis de Sales:
"As God created us in his own image and likeness, he ordained that our love for one another should be in the image and likeness of the love we owe him, our God. He said: You must love the Lord your God, with your whole heart, and with your whole soul, and with your whole mind. This is the greatest, and the first commandment. And the second is like it: You must love your neighbor as yourself.
Why do we love God? ‘The reason for loving God,’ says St. Bernard, ‘is God himself;’ as though he had said: we love God because he is the supreme and infinite goodness. And why do we love ourselves? Surely because we are the image and likeness of God; and since all men and women possess this same dignity, we love them also as ourselves, that is, as holy and living images of the Godhead.
For it is on that account that we belong to God through a kinship so close and a dependence so lovable, that he does not hesitate to call himself our Father, and to call us his children; it is on that account that we are capable of being united to him by the fruition of his sovereign goodness and joy; it is on that account that we receive his grace, that our spirits are associated to his most Holy Spirit, and made in a sense ‘sharers in the divine nature,’ as St. Leo says.
And therefore the same charity which produces the acts of the love of God, produces at the same time those of the love of our neighbor. And even as Jacob saw that one same ladder touched heaven and earth, serving the angels both for descending and ascending, so we know that one same charity cherishes both God and our neighbor, raising us to spiritual union with God, and bringing us back again to loving companionship with our neighbors; always, however, on the understanding that we love our neighbor as being after the image and likeness of God, created to have communication with the divine goodness, to participate in his grace, and to enjoy his glory.
This is why divine love not only repeatedly commands us to love our neighbors, but also itself produces this love and pours it into our hearts, since they bear its own image and likeness; for just as we are the image of God, so our holy love for one another is the true image of our heavenly love for God.”