"God created man in his image... male and female he created them" (Gn 1:27)
Married love particularly reveals its true nature and nobility when we realize that it takes its origin from God, who is love... Marriage, then, is far from being the effect of chance or the result of the blind evolution of natural forces. It is in reality the wise and provident institution of God the Creator, whose purpose was to effect in man His loving design. As a consequence, husband and wife, through that mutual gift of themselves alone... develop that union of two persons in which they perfect one another, cooperating with God in the generation and rearing of new lives. The marriage of those who have been baptized is, in addition, invested with the dignity of a sacramental sign of grace, for it represents the union of Christ and His Church (Eph 5:32).
In the light of these facts the characteristic features and exigencies of married love are clearly indicated. This love is above all fully human, a compound of sense and spirit. It is not, then, merely a question of natural instinct or emotional drive. It is also, and above all, an act of the free will, whose trust is such that it is meant not only to survive the joys and sorrows of daily life, but also to grow, so that husband and wife become in a way one heart and one soul, and together attain their human fulfillment.
It is a love which is total—that very special form of personal friendship in which husband and wife generously share everything, allowing no unreasonable exceptions and not thinking solely of their own convenience. Whoever really loves his partner loves not only for what he receives, but loves that partner for the partner's own sake, content to be able to enrich the other with the gift of himself.
Married love is also faithful and exclusive of all other, and this until death. This is how husband and wife understood it on the day on which, fully aware of what they were doing, they freely vowed themselves to one another in marriage... Finally, this love is fecund. It is not confined wholly to the loving interchange of husband and wife; it also contrives to go beyond this to bring new life into being.