The Sacrament of Matrimony or Marriage is the sacramental binding covenant between one man and one woman in which they agree to eternal fidelity to each other and commit to being God's partners in the creation of new life. Marriage is the only sacrament that the couple actually administers to one another. The priest is only a witness.
The Sacrament of Marriage is a covenant, which is more than a contract. Covenant always expresses a relationship between persons. The marriage covenant refers to the relationship between the husband and wife, a permanent union of persons capable of knowing and loving each other and God. The celebration of marriage is also a liturgical act, appropriately held in a public liturgy at church. Catholics are urged to celebrate their marriage within the Eucharistic Liturgy. By their marriage, the couple witnesses Christ's spousal love for the Church. One of the Nuptial Blessings in the liturgical celebration of marriage refers to this in saying, "Father, you have made the union of man and wife so holy a mystery that it symbolizes the marriage of Christ and his Church."
The Catholic Church teaches that marriage between two baptized persons is a sacrament. The couple’s relationship expresses, in a unique way, the unbreakable bond of love between Christ and his people. Like the other six sacraments of the Church, marriage is a sign or symbol which reveals the Lord Jesus and through which his divine life and love are communicated. All seven sacraments were instituted by Christ and were entrusted to the Church to be celebrated in faith within and for the community of believers. The rituals and prayers by which a sacrament is celebrated serve to express visibly what God is doing invisibly. In the Sacrament of Marriage, God’s love becomes present to the spouses in their total union with and through the Holy Spirit. As the couple goes through ups and downs on the journey of life with God in the center of their marriage, they become more able to give and receive from each other. As they cooperate with Christ in their lives, their lives become Sacramental and unconditionally bonded to Him, through Him.