21 If then to sin, that others may not commit a worse sin, either against us or against any, without doubt we ought not; it is to be considered in that which Lot did, whether it be an example which we ought to imitate, or rather one which we ought to avoid. For it seems meet to be more looked into and noted, that, when so horrible an evil from the most flagitious impiety of the Sodomites was impending over his guests, which he wished to ward off and was not able, to such a degree may even that just man's mind have been disturbed, that he was willing to do that which, not man's fear with its misty temper, but God's Law in its tranquil serenity, if it be consulted by us, will cry aloud, must not be done, and will command rather that we be so cautious not to sin ourselves, that we sin not through fear of any sins whatever of other men.
For that just man, by fearing other men's sins, which cannot defile except such as consent thereto, was so perturbed that he did not attend to his own sin, in that he was willing to subject his daughters to the lusts of impious men. These things, when we read in holy Scriptures, we must not, for that we believe them done, therefore believe them meet to be done; lest we violate precepts while we indiscriminately follow precedents. Or, truly, because David swore to put Nabal to death, and, upon more considerate clemency, did it not, shall we therefore say that he is to be imitated, so that we may swear to do a thing which afterwards we may see to be not meet to be done?
But as fear perturbed the one, so that he was willing to prostitute his daughters, so did anger the other, that he swore rashly. In short, if it were allowed us to inquire of them both, by asking them to tell us why they did these things, the one might answer, “Fearfulness and trembling came upon me, and darkness covered me;” the other too might say, “My eye was troubled through wrath:” so that we should not marvel either that the one in the darkness of fear, or the other with troubled eye, saw not what was meet to have been seen, that they might not do what was not meet to have been done.
Source: To Consentius: Against Lying (New Advent)