When Jesus elevated marriage to the dignity of a sacrament he was building upon the existing natural reality that man and woman were made for union with one another in marriage. God made them male and female and from the beginning the institution of marriage has been for the benefit of the spouses and the loving care of their children. It is a faithful, exclusive, lifelong union of a man and a woman joined in an intimate community of life and love that is open to children and is the most basic unit of human society.
Because marriage is a vocation that involves both the help of grace from God and the cooperation of the spouses with one another, the Church has required various amounts of preparation for the engaged to help them be well equipped for their new life together. Marriage preparation takes many different forms throughout the world because the needs of couples are different according to culture and circumstances. Once entered, marriage is a permanent state of life which requires sacrifice and commitment. For this reason the Church seeks to help the engaged not only learn useful skills and grow in their relationship with one another and with God, she also assists them in making a good decision to marry so that they can be ready to say "I do" and commit to living out the full expression of married love. Couples who make the most of the time of their engagement find themselves more ready for the challenges that lie ahead for them in the exciting adventure of marriage and family life.
It is perhaps best to let this answer come directly from the Compendium of the Catechism of the Catholic Church, 349:
"The Church, since she is faithful to her Lord, cannot recognize the union of people who are civilly divorced and remarried. 'Whoever divorces his wife and marries another, commits adultery against her; and if she divorces her husband and marries another, she commits adultery' (Mark 10:11-12). The Church manifests an attentive solicitude toward such people and encourages them to a life of faith, prayer, works of charity and the Christian education of their children. However, they cannot receive sacramental absolution, take Holy Communion, or exercise certain ecclesial responsibilities as long as their situation, which objectively contravenes God's law, persists."
Pope Francis: Marriage Preparation is Important
Why Have a Catholic Wedding?
Christ himself elevated the natural institution of marriage to the dignity of a sacrament during his public ministry.
He worked his first miracle at a wedding (John 3:1-11) and he taught that marriage in the New Covenant is permanent and holy (Matthew 19:3-9). The apostles taught on the beauty and significance of marriage throughout the New Testament (1 Peter 3:1-12). St. Paul even taught (Ephesians 5:21-33) on the mystery of the relationship between the members of the Church and Christ the bridegroom as analogous to the relationship between husband and wife in the sacrament of Marriage.
Christian Marriage is a sacrament that orders the husband and wife to serve one another. This service is based on the Christian virtue of charity and is done in a spirit of care and concern for the good of the spouse and child(ren) following the example of Christ. If this sacrament provides grace for salvation to the individual, it is only as a secondary fruit. The principle effect of the grace of the sacrament serves to strengthen the couple’s unity and deepen their love and affection so that their loving service assist them in growing closer to God. The ultimate goal of marriage is the same as Christian life; to respond to God’s grace and be happy with Him in heaven forever.
Made to love… made for family
God is the source of love and so his role in the family is irreplaceable. In fact, “man would not exist were he not created by God’s love and constantly preserved by it.” (Pastoral Constitution on the Church in the Modern World, 19) What is a family? More importantly what is the Christian family? It is the loving union of one man and one woman with the purpose of the procreation and upbringing of children. In the Christian view marriage is a sacrament, instituted by Christ.
Some Pharisees approached him, and tested him, saying, ‘Is it lawful for a man to divorce his wife for any cause whatever?’ He said in reply, ‘Have you not read that from the beginning the Creator ‘made them male and female’ and said, ‘For this reason a man shall leave his father and mother and be joined to his wife, and the two shall become one flesh’? So they are no longer two, but one flesh. Therefore, what God has joined together, no human being must separate.’ They said to him, ‘Then why did Moses command that the man give the woman a bill of divorce and dismiss [her]?’ He said to them, ‘Because of the hardness of your hearts Moses allowed you to divorce your wives, but from the beginning it was not so. I say to you, whoever divorces his wife (unless the marriage is unlawful) and marries another commits adultery.” -Matthew 19: 3-9
The purpose of marriage serves not only the care of children, but also the “communion and good of the couple.” (Compendium of the Catechism, 338) The institution of the family has been the foundation of society throughout human history. The family passes on culture, customs and faith to each generation. Put simply, where the family goes, there goes society. Members of the modern family face an uphill battle to remain faithful to the sacred trust they have received from God to be a living school of love. As Vatican II emphatically stated: “The well-being of the individual person and of human and Christian society is intimately linked with the healthy condition of… marriage and family.” (Vatican II, Pastoral Constitution on the Church, 47).
The Catholic family and fidelity
The Church is God's family in the world.” -Benedict XVI, Deus Caritas Est, 25
In this family there are four units. The largest unit is the universal Church led by the pope. Then there is the diocese with the bishop as its head. Next is the parish with the pastor as its ‘father’. The smallest unit is the domestic church; the Catholic family led by the mother and father who work together to lead each other and their children in striving for holiness. “Christians and all men who hold [the family] in high esteem sincerely rejoice in the various ways by which men today find help in fostering this community of love and perfecting its life, and by which parents are assisted in their lofty calling” (Vatican II, Pastoral Constitution on the Church, 47). Support for family life is of highest importance for Catholics.
Marriage requires mutual fidelity for life. The permanence of the marital bond gives spouses the freedom of marital life lived without fear of abandonment and helps them to persevere in fidelity to one another and to God.
The key to understanding the indissoluble (permanent) character of marriage is not to see it as a rule imposed from the outside, but instead as an essential promise which flows from the vows and nature of marriage. “To opt for marriage in this way expresses a genuine and firm decision to join paths, come what may. Committing oneself exclusively and definitively to another person always involves a risk and a bold gamble.” (Pope Francis, The Joy of Love, 132) In this sense marriage may be the riskiest thing one can do in the course of one’s life. However, it is worth the risk because, “this ‘yes’ tells them that they can always trust one another, and that they will never be abandoned when difficulties arise or new attractions or selfish interests present themselves.” (Pope Francis, The Joy of Love, 132)
Difficult situations: the family under attack
As it has been since the beginning when after “the two became one flesh” they were tempted by the serpent; marriage remains Satan’s favorite target. Today the beauty of family life “is not everywhere reflected with equal brilliance, since polygamy, the plague of divorce, so-called free love and other disfigurements have an obscuring effect. In addition, married love is too often profaned by excessive self-love, the worship of pleasure and illicit practices” like contraception, sterilization and abortion (Vatican II, Pastoral Constitution on the Church, 47).
God’s plan for the family
Vatican II expresses the beauty of marital love and family life which “are ordained for the procreation and education of children, and find in them their ultimate crown“ (Vatican II, Pastoral Constitution on the Church, 48). St. John Paul II helped write The Pastoral Constitution of the Church (Gaudium et Spes), the Second Vatican Council document which teaches about the truth of the Catholic family as the ‘domestic church’. In his work to implement the council he wrote an Apostolic Exhortation where he said: “The Church is deeply convinced that only by the acceptance of the Gospel are the hopes that man legitimately places in marriage and in the family capable of being fulfilled.” (Familiaris Consortio, 3) God’s plan for the Catholic family is to participate in the work of the Church “becoming a saved community… called upon to communicate Christ's love to their brethren, thus becoming a saving community.” (Familiaris Consortio, 49).
We discover the meaning of life through contact with God’s revelation and we learn what it means to be human in the family because “the family is a kind of school of deeper humanity” (Vatican II, Pastoral Constitution on the Church, 51). Seen in this light the family is the school and love is the lesson. We normally first learn to love God and one another as we grow up in our family. And even though our families are not perfect, they nevertheless are true schools of love. In fact, “authentic married love is caught up into divine love and is governed and enriched by Christ's redeeming power and the saving activity of the Church, so that this love may lead the spouses to God with powerful effect and may aid and strengthen them in the sublime office of being a father or a mother” (Vatican II, Pastoral Constitution on the Church, 48). As a ‘school’, “the family has the mission to guard, reveal and communicate love” (Familiaris Consortio, 17).
The family: school of prayer and faith
As a school of love the family is also a school of prayer where, “inspired by the example and family prayer of the their parents, children… will more easily set out upon the path of a truly human training, of salvation, and of holiness” (Vatican II, Pastoral Constitution on the Church, 48). In the letter to the Philippians St. Paul offers a prayer fitting for the family: “it is my prayer that your love may abound more and more, with knowledge and all discernment, so that you may approve what is excellent, and may be pure and blameless for the day of Christ.” (Philippians 1: 9-10) For families beset by difficulties, prayer in the home has the power to change things for the better.
As the now famous saying goes:
The family that prays together, stays together.”
Because of this truth, “parents have the specific responsibility of educating their children in prayer, introducing them to gradual discovery of the mystery of God and to personal dialogue with Him” (Familiaris Consortio, 60). Parents should also “eagerly carry out their duties of education, especially religious education, which is primarily entrusted to them” (Vatican II, Pastoral Constitution on the Church, 48). And because, “there is no family that does not know how selfishness, discord, tension and conflict violently attack and at times mortally wound its own communion” familial religious formation must focus on “family communion [which] can only be preserved and perfected through a great spirit of sacrifice. It requires, in fact, a ready and generous openness of each and all to understanding, to forbearance, to pardon, to reconciliation” (Familiaris Consortio, 21).