23 This conjugal faith, however, which is most aptly called by St. Augustine the "faith of chastity" blooms more freely, more beautifully and more nobly, when it is rooted in that more excellent soil, the love of husband and wife which pervades all the duties of married life and holds pride of place in Christian marriage. For matrimonial faith demands that husband and wife be joined in an especially holy and pure love, not as adulterers love each other, but as Christ loved the Church. This precept the Apostle laid down when he said: "Husbands, love your wives as Christ also loved the Church," that Church which of a truth He embraced with a boundless love not for the sake of His own advantage, but seeking only the good of His Spouse. The love, then, of which We are speaking is not that based on the passing lust of the moment nor does it consist in pleasing words only, but in the deep attachment of the heart which is expressed in action, since love is proved by deeds. This outward expression of love in the home demands not only mutual help but must go further; must have as its primary purpose that man and wife help each other day by day in forming and perfecting themselves in the interior life, so that through their partnership in life they may advance ever more and more in virtue, and above all that they may grow in true love toward God and their neighbor, on which indeed "dependeth the whole Law and the Prophets." For all men of every condition, in whatever honorable walk of life they may be, can and ought to imitate that most perfect example of holiness placed before man by God, namely Christ Our Lord, and by God's grace to arrive at the summit of perfection, as is proved by the example set us of many saints.
Source: Casti Connubii (Vatican.va)