105 Consequently, since everything must be referred to the law and mind of God, in order to bring about the universal and permanent restoration of marriage, it is indeed of the utmost importance that the faithful should be well instructed concerning matrimony; both by word of mouth and by the written word, not cursorily but often and fully, by means of plain and weighty arguments, so that these truths will strike the intellect and will be deeply engraved on their hearts. Let them realize and diligently reflect upon the great wisdom, kindness and bounty God has shown towards the human race, not only by the institution of marriage, but also, and quite as much, by upholding it with sacred laws; still more, in wonderfully raising it to the dignity of a Sacrament by which such an abundant fountain of graces has been opened to those joined in Christian wedlock, that these may be able to serve the noble purposes of wedlock for their own welfare and for that of their children, of the community and also for that of human relationship.
Source: Casti Connubii (Vatican.va)