Why be faithful?
Love wants to be permanent. It cannot be ‘until further notice’. “This intimate union, the reciprocal gift of two people, no less than the good of the children, demands entire fidelity of the spouses and requires their indissoluble unity.”
The deepest reason is to be found in the fidelity of God to his covenant, of Christ to his Church. Through the sacrament of marriage, the spouses are authorised to represent this fidelity and to bear witness to it. Through the sacrament, the indissolubility of marriage receives a new and deeper meaning.
It can seem difficult, even impossible, to commit to another human being for life. It is all the more important to announce the Gospel, since God loves us with a permanent and irrevocable love, since spouses partake in this love, which carries and supports them, and since through their fidelity they can be witnesses to God’s faithful love. The spouses, who with the grace of God bear witness to this, often in very difficult situations, deserve the gratitude and support of the church community.
(Catechism of the Catholic Church in 1646, 1647, 1648)