In his encyclical Casti Connubii (On Christian Marriage), Pope Pius XII defined the foremost responsibility of husband and wife in marriage:
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.
This mutual molding of husband and wife, this determined effort to perfect each other, can in a very real sense, as the Roman Catechism teaches, be said to be the chief reason and purpose of matrimony, provided matrimony be looked at not in the restricted sense as instituted for the proper conception and education of the child, but more widely as the blending of life as a whole and the mutual interchange and sharing thereof.
Thus, the principle end of marriage is the mutual assistance of spouses in growing in holiness with the goal of reaching heaven.
Marriage is under attack. Satan wants to destroy the family in an attempt to keep souls from reaching heaven. God has chosen to use marriage as an image of Christ’s love for His bride, the Church (Eph 5:25-32). If Satan can destroy marriage, he is destroying the one thing that images God’s love for His people. We need to be praying for the protection of all families from the onslaught of the evil one.
To that end, we offer the following prayer of Venerable Pope Pius XII for the building up of strong, holy, and healthy marriages and families.
Prayer for Families
O Lord, God of goodness and mercy, Who in the midst of an evil and sinful world hast presented to the society of the redeemed the Holy Family of Nazareth as a spotless mirror of piety, justice and love, behold how the family is being undermined on all sides, every effort being made to desecrate it by stripping it of faith, religion and morals.
Regard the work of Thy own hands. Safeguard in our homes the domestic virtues, for these alone will ensure us harmony and peace. Come and stir up the champions of the family. Bestir the modern apostles so that in Thy Name, bearing the message of Jesus Christ and exhibiting holiness of life, they may revive the doctrines of conjugal fidelity for married couples, the exercise of authority by parents, obedience on the part of children and modesty on the part of girls. Grant also through the efforts of these apostles, that the home favoured by Thee with many blessings may again become an object of esteem and love in the minds and hearts of all.
It is through the examples of the Divine model of Nazareth that the Christian family is to be restored in Jesus Christ and to recover its former respect and dignity. Then every home will again become a sanctuary and in every household will be rekindled the flame of faith to teach patience in adversity and moderation in prosperity and to promote order, peace and harmony in all things.
Under Thy paternal gaze, O Lord, and with confidence in Thy Providence and in the loving patronage of Jesus, Mary and Joseph, the family will become a sanctuary of virtue and a school of wisdom. It shall prove, as Christ has promised, a haven of rest against life’s burdens. In the sight of the world it shall render glory to Thee, O Father, and to Thy Son, Jesus, until the day when, through Him, we shall, together with all His members, sing the Divine praises in the eternal ages to come. Amen.
 Pius XII, Encyclical Letter Casti Connubii, (December 31, 1930), internet: https://w2.vatican.va/content/pius-xi/en/encyclicals/documents/hf_p-xi_enc_19301231_casti-connubii.html, §23-24 (accessed August 1, 2019).