54 But now, to conclude by summing up this passage, what can be named or thought of more laborious and toilsome, where the believing soul is straining every nerve of its industry, than the subduing of vicious habit? Let such an one cut off the members which obstruct the kingdom of heaven, and not be overwhelmed by the pain: in conjugal fidelity let him bear with everything which, however grievously annoying it may be, is still free from the guilt of unlawful corruption, i.e. of fornication: as, for instance, if any one should have a wife either barren, or misshapen in body, or faulty in her members—either blind, or deaf, or lame, or having any other defect—or worn out by diseases and pains and weaknesses, and whatever else may be thought of exceeding horrible, fornication excepted, let him endure it for the sake of his plighted love and conjugal union; and let him not only not put away such a wife, but even if he have her not, let him not marry one who has been divorced by her husband, though beautiful, healthy, rich, fruitful. And if it is not lawful to do such things, much less is it to be deemed lawful for him to come near any other unlawful embrace; and let him so flee from fornication, as to withdraw himself from base corruption of every sort. Let him speak the truth, and let him commend it not by frequent oaths, but by the probity of his morals; and with respect to the innumerable crowds of all bad habits rising up in rebellion against him, of which, in order that all may be understood, a few have been mentioned, let him betake himself to the citadel of Christian warfare, and let him lay them prostrate, as if from a higher ground. But who would venture to enter upon labours so great, unless one who is so inflamed with the love of righteousness, that, as it were utterly consumed with hunger and thirst, and thinking there is no life for him till that is satisfied, he puts forth violence to obtain the kingdom of heaven? For otherwise he will not be able bravely to endure all those things which the lovers of this world reckon toilsome and arduous, and altogether difficult in getting rid of bad habits. “Blessed,” therefore, “are they which do hunger and thirst after righteousness: for they shall be filled.”
55. But yet, when any one encounters difficulty in these toils, and advancing through hardships and roughnesses surrounded with various temptations, and perceiving the troubles of his past life rise up on this side and on that, becomes afraid lest he should not be able to carry through what he has undertaken, let him eagerly avail himself of the counsel that he may obtain assistance. But what other counsel is there than this, that he who desires to have divine help for his own infirmity should bear that of others, and should assist it as much as possible? And so, therefore, let us look at the precepts of mercy. The meek and the merciful man, however, seem to be one and the same: but there is this difference, that the meek man, of whom we have spoken above, from piety does not gainsay the divine sentences which are brought forward against his sins, nor those statements of God which he does not yet understand; but he confers no benefit on him whom he does not gainsay or resist. But the merciful man in such a way offers no resistance, that he does it for the purpose of correcting him whom he would render worse by resisting.
Source: Our Lord's Sermon on the Mount (New Advent)