The Catechism in Questions & Answers

346. What does the Sixth Commandment mean for us today?

Marriage is intended to be permanent (cf. Matthew 19: 6; Mark 10: 9). In view of this, it is advisable to protect and promote marriage.
The commandment also implies that both partners should be devoted to one another in faithfulness. The obligations arising from the commandment include the sincere endeavour on the part of both partners to pursue their path of life together in love and the fear of God.