From Of the Good of Marriage.
1. Forasmuch as each man is a part of the human race, and human nature is something social, and has for a great and natural good, the power also of friendship; on this account God willed to create all men out of one, in order that they might be held in their society not only by likeness of kind, but also by bond of kindred. Therefore the first natural bond of human society is man and wife. Nor did God create these each by himself, and join them together as alien by birth: but he created the one out of the other, setting a sign also of the power of the union in the side, whence she was drawn, was formed. For they are joined one to another side by side, who walk together, and look together whither they walk. Then follows the connection of fellowship in children….
4. There is this further, that in that very debt which married persons pay one to another … they owe faith alike one to another. Unto which faith the Apostle allows so great right, as to call it “power,” saying, “The woman has not power of her own body, but the man; again in like manner also the man has not power of his own body, but the woman.” But the violation of this faith is called adultery, when either by instigation of one’s own lust, or by consent of lust of another, there is sexual intercourse on either side with another against the marriage compact: and thus faith is broken, which, even in things that are of the body, and mean, is a great good of the soul: and therefore it is certain that it ought to be preferred even to the health of the body, wherein even this life of ours is contained. …..
6. ….. Therefore married persons owe one another not only the faith of their sexual intercourse itself, for the begetting of children, which is the first fellowship of the human kind in this mortal state; but also, in a way, a mutual service of sustaining one another’s weakness, in order to shun unlawful intercourse: so that, although perpetual continence be pleasing to one of them, he may not, save with consent of the other. For thus far also, “The wife has not power of her own body, but the man; in like manner also the man has not power of his own body, but the woman.” …..
8. “Honorable,” therefore, “is marriage in all, and the bed undefiled.” …..
11. ….. But now what shall we say against the most plain speech of the Apostle, saying, “Let her do what she will; she sins not, if she be married;” and, “If you shall have taken a wife, you have not sinned: and, if a virgin shall have been married, she sins not.” …..
18. For what food is unto the conservation of the man, this sexual intercourse is unto the conservation of the race: and both are not without carnal delight: which yet being modified, and by restraint of temperance reduced unto the use after nature, cannot be lust. But what unlawful food is in the supporting of life, this sexual intercourse of fornication or adultery is in the seeking of a family. And what unlawful food is in luxury of belly and throat, this unlawful intercourse is in lust that seeks not a family. ….. It is better to die without children, than to seek a family from unlawful intercourse. But from whatever source men be born, if they follow not the vices of their parents, and worship God aright, they shall be honest and safe. For the seed of man, from out what kind of man soever, is the creation of God, and it shall fare ill with those who use it ill, yet shall not, itself at any time be evil. But as the good sons of adulterers are no defense of adulteries, so the evil sons of married persons are no charge against marriage. …..
24. Marriage, I say, is a good, and may be, by sound reason, defended against all calumnies. …..