A marriage is established by the marriage
covenant, the irrevocable consent that the spouses freely give to and
receive from each other. This unique union of a man and woman and the
good of the children impose total fidelity on each of them and the
unbreakable unity of their bond. To make the indissoluble marriage
covenant a clearer sign of this full meaning and a surer help in its
fulfillment, Christ the Lord raised it to the dignity of a sacrament,
modeled on his own nuptial bond with the Church.
-The Rite of Marriage