38 Certain it is, albeit all this disputation go from side to side, some asserting that it is never right to lie, and to this effect reciting divine testimonies: others gainsaying, and even in the midst of the very words of the divine testimonies seeking place for a lie; yet no man can say, that he finds this either in example or in word of the Scriptures, that any lie should seem a thing to be loved, or not had in hatred; howbeit sometimes by telling a lie you must do that you hate, that what is more greatly to be detested may be avoided.
But then here it is that people err; they put the precious beneath the vile. For when you have granted that some evil is to be admitted, that another and more grievous may not be admitted; not by the rule of truth, but by his own cupidity and custom does each measure the evil, accounting that to be the more grievous, which himself more greatly dreads, not which is in reality more greatly to be fled from. All this fault is engendered by perversity of loving. For being there are two lives of ours; the one eternal, which is promised of God; the other temporal, in which we now are: when a man shall have begun to love this temporal more than that eternal, for the sake of this which he loves he thinks all things right to be done; and there are not any, in his estimation, more grievous sins than those which do injury to this life, and either take away from it any commodity unjustly and unlawfully, or by inflicting of death take it utterly away.
And so thieves, and robbers, and ruffians, and torturers, and slayers, are more hated of them than lascivious, drunken, luxurious men, if these molest no man. For they do not understand or at all care, that these do wrong to God; not indeed to any inconvenience of Him, but to their own pernicious hurt; seeing they corrupt His gifts bestowed upon them, even His temporal gifts, and by their very corruptions turn away from eternal gifts: above all, if they have already begun to be the Temple of God; which to all Christians the Apostle says thus: “Do you not know that you are the temple of God, and that the Spirit of God dwells in you? Whoso shall corrupt God's temple, God will corrupt him. For the temple of God is holy: which temple are you.”
Source: On Lying (New Advent)