And he has a third grievous snare; as when he invests the sin with a show of devotion. And where has the devil so far prevailed as to deceive to this degree? Hear, and beware of his devices. Christ by Paul commanded “that a woman depart not from her husband, and not to defraud one another, except by consent;” but some from a love of continence forsooth, having withdrawn from their own husbands, as though they were doing something devout, have driven them to adultery. Consider now what an evil it is that they, undergoing so much toil, should be blamed as having committed the greatest injustice, and should suffer extreme punishment, and drive their husbands into the pit of destruction.
Others again, abstaining from meats by a rule of fasting, have by degrees gone so far as to abhor them; which even of itself brings a very great punishment.
But this comes to pass, when any hold fast their own prejudices contrary to what is approved by the Scriptures. Those also among the Corinthians thought it was a part of perfection to eat of all things without distinction, even of things forbidden, but nevertheless this was not of perfection, but of the utmost lawlessness. Wherefore also Paul earnestly reproves them, and pronounces them to be worthy of extreme punishment. Others again think it a sign of piety to wear long hair. And yet this is among the things forbidden, and carries with it much disgrace.
Again, others follow after excessive sorrow for their sins as a profitable thing; yet it also comes of the devil's wiles, and Judas showed it; at least in consequence thereof he even hanged himself. Therefore Paul again was in fear about him that had committed fornication, lest any such thing should befall him, and persuaded the Corinthians speedily to deliver him, “lest perhaps such a one should be swallowed up with overmuch sorrow.” Then, indicating that such a result comes of the snares of that wicked one, he says, “Lest Satan should get an advantage over us, for we are not ignorant of his devices,” meaning that he assails us with much craft. Since if he fought against us plainly and openly, the victory would be ready and easy; or rather even now, if we be vigilant, victory will be ready. For indeed against each one of those ways God has armed us.
For to persuade us not to despise even these little things, hear what warning He gives us, saying, “He that says to his brother, thou fool, shall be in danger of hell;” and he that has looked with unchaste eyes is a complete adulterer. And on them that laugh he pronounces a woe, and everywhere He removes the beginning and the seeds of evil, and says we have to give an account of an idle word. Therefore also Job applied a remedy even for the thoughts of his children.
But about not despairing, it is said, “Does he fall, and not arise? Does he turn away, and not return?” and, “I do not will the death of the sinner, so much as that he should turn and live:” and, “Today if you will hear His voice:” and many other such things, both sayings and examples are set in the Scripture. And in order not to be ruined under the guise of godly fear, hear Paul saying, “Lest perhaps such a one be swallowed up by overmuch sorrow.”
Knowing therefore these things, let us set for a barrier in all the ways that pervert the unwary the wisdom which is drawn from the Scriptures. Neither say, why, what is it, if I gaze curiously at a beautiful woman? For if you should commit the adultery in the heart, soon you will venture on that in flesh. Say not, why, what is it if I should pass by this poor man? For if you pass this man by, you will also the next; if him, then the third.
Neither again say, why, what is it, if I should desire my neighbor's goods. For this, this caused Ahab's ruin; although he would have paid a price, yet he took it from one unwilling. For a man ought not to buy by force, but on persuasion. But if he, who would have paid the fair price, was so punished, because he took from one unwilling, he who does not so much as this, and takes by violence from the unwilling, and that when living under grace, of what punishment will he not be worthy?
In order therefore that we be not punished, keeping ourselves quite pure from all violence and rapine, and guarding against the sources of sins together with the sins themselves, let us with much diligence give heed to virtue; for thus shall we also enjoy the good things eternal by the grace and love towards man of our Lord Jesus Christ, to whom be glory world without end. Amen.
Source: Homilies on the Gospel of St. Matthew (New Advent)