Catechism of the Catholic Church §1645 — excerpt
"The unity of marriage, distinctly recognized by our Lord, is made clear in the equal personal dignity which must be accorded to man and wife in mutual and unreserved affection."
This translation is under copyright, so only the cited words are quoted here. Follow the link for the full text. Translation: English translation of the Catechism of the Catholic Church, 2nd ed. (Libreria Editrice Vaticana), as posted at vatican.va.
Also cites: GS 49 # 2 · FC 19