Marriage as a Sacrament
A sacrament is a visible sign of an invisible reality. Matrimony is a sacrament and as such it is a sign to the world of the invisible God living in our midst - the living God who bears fruit in the lives of two people. They are a continual sign of His Power in the world. There is special grace and power within every couple God has joined together. Everything they do singly or together, is a living out of their sacrament... AlI the facets of life together have power hidden within them to make them holy. Married life is the ground of holiness, love is the seed planted by God.
God who created man out of love also calls him to love—the fundamental and innate vocation of every human being. For man is created in the image and likeness of God who is himself love. Since God created him man and woman, their mutual love becomes an image of the absolute and unfailing love with which God loves man. It is good, very good, in the Creator's eyes. And this love which God blesses is intended to be fruitful and to be realized in the common work of watching over creation: "And God blessed them, and God said to them: ‘Be fruitful and multiply, and fill the earth and subdue it."
Holy Scripture affirms that man and woman were created for one another: "It is not good that the man should be alone." The woman, "flesh of his flesh," his equal, his nearest in all things, is given to him by God as a "helpmate"; she thus represents God from whom comes our help. "Therefore a man leaves his father and his mother and cleaves to his wife, and they become one flesh." The Lord himself shows that this signifies an unbreakable union of their two lives by recalling what the plan of the Creator had been "in the beginning": "So they are no longer two, but one flesh."
The Catechism of the Catholic Church