Marriage under the pedagogy of the Law
Seeing God's covenant with Israel in the image of exclusive and faithful married love, the prophets prepared the Chosen People's conscience for a deepened understanding of the unity and indissolubility of marriage. The books of Ruth and Tobit bear moving witness to an elevated sense of marriage and to the fidelity and tenderness of spouses. Tradition has always seen in the Song of Solomon a unique expression of human love, a pure reflection of God's love - a love "strong as death" that "many waters cannot quench."
Source: Catechism of the Catholic Church (Vatican.va)