From Traditi Humilitati, on Marriage:
10. We also want you to imbue your flock with reverence for the sanctity of marriage so that they may never do anything to detract from the dignity of this sacrament. They should do nothing that might be unbecoming to this spotless union nor anything that might cause doubt about the perpetuity of the bond of matrimony. This goal will be accomplished if the Christian people are accurately taught that the sacrament of matrimony ought to be governed not so much by human law as by divine law and that it ought to be counted among sacred, not earthly, concerns. Thus, it is wholly subject to the Church. Formerly marriage had no other purpose than that of bringing children into the world. But now it has been raised to the dignity of a sacrament by Christ the Lord and enriched with heavenly gifts. Now its purpose is not so much to generate offspring as to educate children for God and for religion. This increases the number of worshippers of the true divinity. It is agreed that the union of marriage signifies the perpetual and sublime union of Christ with His Church; as a result, the close union of husband and wife is a sacrament, that is, a sacred sign of the immortal love of Christ for His spouse. Therefore, teach the people what is sanctioned and what is condemned by the rules of the Church and the decrees of the Councils. Also explain those things which pertain to the essence of the sacrament. Then they will be able to accomplish those things and will not dare to attempt what the Church detests. We ask this earnestly of you because of your love of religion.