On the threshold of his public life Jesus performs his first sign—at his mother’s request—during a wedding feast. The Church attaches great importance to Jesus’ presence at the wedding at Cana. She sees in it the confirmation of the goodness of marriage and the proclamation that thenceforth marriage will be an efficacious sign of Christ’s presence.…
This is what the Apostle Paul makes clear when he says: “Husbands, love your wives, as Christ loved the church and gave himself up for her, that he might sanctify her,” adding at once: “For this reason a man shall leave his father and mother and be joined to his wife, and the two shall become one. This is a great mystery, and I mean in reference to Christ and the Church.”
The entire Christian life bears the mark of the spousal love of Christ and the Church. Already Baptism, the entry into the People of God, is a nuptial mystery… which precedes the wedding feast, the Eucharist. Christian marriage in its turn becomes an efficacious sign, the sacrament of the covenant of Christ and the Church. Since it signifies and communicates grace, marriage between baptized persons is a true sacrament of the New Covenant.
-From the Catechism of the Catholic Church