During the general audience in St Peter's Square on Wednesday, he explained that in addition to the legal, psychological and moral advice given to couples before marriage, spiritual preparation should also be offered.
According to the Pope in his remarks in front of thousands of pilgrims, this is primarily about the role that the Holy Spirit can play in a marriage.
Just as Jesus turned water into wine at the wedding of Cana, the Holy Spirit can also work miracles in a marriage if the couple turn to him in prayer.
"He can transform the water of habit into a new joy of togetherness," explained Francis.
Marriage is - like the divine Trinity - a mutual gift of man and woman. The spouses also form a common "subject in the plural".
Before the world and their children, they would become a common subject, a "we".
The Pope emphatically warned against "marriages built on sand".
Their consequences are obvious, he said, and the consequences of the resulting separations are usually borne by the children.