Chapter 22 — Part II: The Sacraments — Matrimony
Section 27. A second reason for marriage is the desire of family, not so much, however, with a view to leave after us heirs to inherit our property and fortune, as to bring up children in the true faith and in the service of God. That such was the principal object of the holy Patriarchs when they married is clear from Scripture. Hence the Angel, when informing Tobias of the means of repelling the violent assaults of the evil demon, says: I will show thee who they are over whom the devil can prevail; for they who in such manner receive matrimony as to shut out God from themselves and from their mind, and to give themselves to their lust, as the horse and mule which have not understanding, over them the devil hath power. He then adds: Thou shalt take the virgin with the fear of the Lord, moved rather for love of children than for lust, that in the seed of Abraham thou mayest obtain a blessing in children. It was also for this reason that God instituted marriage from the beginning; and therefore married persons who, to prevent conception or procure abortion, have recourse to medicine, are guilty of a most heinous crime -- nothing less than wicked conspiracy to commit murder.