Near the end of dz 2232 casti connubii says "this mutual interior formation of husband and wife, this constant zeal for bringing each other to perfection, in a very true sense, as the roman catechism teaches, can be said to be the very first reason and purpose of matrimony; if, however, matrimony be not accepted too narrowly as instituted for the proper procreation and education of children, but more broadly as the mutual participation in all life, companionship, and association."
What exactly is this saying? This is under the section speaking about the blessings of marriage. And, this is under blessing number two, which is the "blessing of faith".