10 We have seen that God's eros for man is also totally agape . This is not only because it is bestowed in a completely gratuitous manner, without any previous merit, but also because it is love which forgives. Hosea above all shows us that this agape dimension of God's love for man goes far beyond the aspect of gratuity. Israel has committed “adultery” and has broken the covenant; God should judge and repudiate her. It is precisely at this point that God is revealed to be God and not man: “How can I give you up, O Ephraim! How can I hand you over, O Israel! ... My heart recoils within me, my compassion grows warm and tender. I will not execute my fierce anger, I will not again destroy Ephraim; for I am God and not man, the Holy One in your midst” ( Hos 11:8-9). God's passionate love for his people—for humanity—is at the same time a forgiving love. It is so great that it turns God against himself, his love against his justice. Here Christians can see a dim prefigurement of the mystery of the Cross: so great is God's love for man that by becoming man he follows him even into death, and so reconciles justice and love. The philosophical dimension to be noted in this biblical vision, and its importance from the standpoint of the history of religions, lies in the fact that on the one hand we find ourselves before a strictly metaphysical image of God: God is the absolute and ultimate source of all being; but this universal principle of creation—the Logos , primordial reason—is at the same time a lover with all the passion of a true love. Eros is thus supremely ennobled, yet at the same time it is so purified as to become one with agape . We can thus see how the reception of the Song of Songs in the canon of sacred Scripture was soon explained by the idea that these love songs ultimately describe God's relation to man and man's relation to God. Thus the Song of Songs became, both in Christian and Jewish literature, a source of mystical knowledge and experience, an expression of the essence of biblical faith: that man can indeed enter into union with God—his primordial aspiration. But this union is no mere fusion, a sinking in the nameless ocean of the Divine; it is a unity which creates love, a unity in which both God and man remain themselves and yet become fully one. As Saint Paul says: “He who is united to the Lord becomes one spirit with him” ( 1 Cor 6:17).
Source: Deus Caritas Est (Vatican.va)