9 Therefore the sacred partnership of true marriage is constituted both by the will of God and the will of man. From God comes the very institution of marriage, the ends for which it was instituted, the laws that govern it, the blessings that flow from it; while man, through generous surrender of his own person made to another for the whole span of life, becomes, with the help and cooperation of God, the author of each particular marriage, with the duties and blessings annexed thereto from divine institution.
Source: Casti Connubii (Vatican.va)