He discusses the duties of a husband toward his wife:
This part is offensive to modern ears:
But if your wife is of a servile condition, rustic and ill-mannered character, that with these pleasant words she is not amended, rebuke her with harsh and sharp words, threats, and other fears. And if this is still not enough, and you see her do something offensive to God, injurious to her soul, your or her shame, or another noteworthy danger, take up the stick and beat her well; because it is better to be scourged in the body and to heal the soul than to lose the body and damn the soul.
And wife toward her husband:
The Franciscan friar delves into the nitty-gritty of marriage, such as superfluously performing coitus, which leads to sickness and shortening one's lifespan:
The first harm is sickness; because many people get sick, weak, and lose the natural force and vigor of nature. Wherefore, Esdras [The non-canonical 3 Esdras 4:26: “And many have become mad for their wives: and have been made bondmen for them”], most learned in the law of God, says that many became insane because of their wives, i.e., because of the superfluous and indiscreet copulation that they had with them. Certainly, it is a great infirmity to lose one’s senses and become insane. The booming Ambrose also says that some have become blind for this same reason. Avicenna also says that one act of coitus harms more than ten phlebotomies, i.e., bloodletting, according to what most learned physicians have told me [R. W. Bernard, Science Discovers the Physiological Value of Continence: “An ounce of semen is considered to be equal in value to sixty ounces of blood, of which it constitutes an extract of some of its most valuable of constituents, as far as its vitalizing power is concerned.”]. We have the example of bulls. Two bulls fighting together, one of them victorious, as if by great happiness finds the cow, and copulates with it. The other bull, who was defeated, by instinct of nature knows that bull had lost some of its strength; immediately it assaults it, and whereas at first it was defeated, in the second battle it wins. Thus, the frequentation of this act makes one lose strength and fall into sickness; he becomes weak and soon becomes old.
Shortening of lifespan
The second harm, which married people have who superfluously perform the marriage act, is the shortening of lifespan. For they do not live so long in the world as they would live if they used such act discreetly. Wherefore, Albert the Great, and even the prince of philosophers, Aristotle, say that elephants live a long time, i.e., one hundred or one hundred twenty years, only because of their continence; because in two years they rest and attend to the carnal act only five or six days. They also say that male sparrows live less than females, because of their overuse of this act. Yet the mule lives for a long time, because it observes continence. Certainly, as this is how it is in animals, so is it in humans, according to their natural condition.