1 Samuel 21:2

No wonder that these dispensations were uprightly made use of in the Old Testament and that holy men sometimes lied in praiseworthy or at least in pardonable fashion, since we see that far greater things were permitted them because it was a time of beginnings. For what is there to wonder at that when the blessed David was fleeing Saul and Ahimelech the priest asked him, "Why are you alone, and no one is with you?" he replied and said, "The king gave me a commission and said, Let no one know the reason why you were sent, for I have also appointed my servants to such and such a place"? And again: "Do you have a spear or a sword at hand? For I did not bring my sword and my weapons with me because the king's business was urgent"? Or what happened when he was brought to Achish, the king of Gath, and made believe that he was insane and raging, and "changed his countenance before them, and fell down between their hands, and dashed himself against the door of the gate, and his spittle ran down his beard"? For, after all, they lawfully enjoyed flocks of wives and concubines, and no sin was imputed to them on this account. Besides that, they also frequently spilled their enemies' blood with their own hands, and this was held not only to be irreprehensible but even praiseworthy.We see that, in the light of the gospel, these things have been utterly forbidden, such that none of them can be committed without very serious sin and sacrilege. Likewise we believe that no lie, in however pious a form, can be made use of by anyone in a pardonable way, to say nothing of praiseworthily, according to the words of the Lord: "Let your speech be yes, yes, no, no. Whatever is more than these is from the evil one." The apostle also agrees with this: "Do not lie to one another."

And David said to Achimelech the priest: "The king has commanded me a certain matter," etc. The Lord said to the apostles, the heirs of the everlasting kingdom and priesthood: "The people of persecutors and unbelievers commanded me, as much as possible, not to call them to faith by teaching. And he said, as it were, in my ears: Let no one know the reason for the envy and plots for which, having left me, you were sent to bring salvation to the nations, and what kind of deceitful commands overflowing with wicked hatred I strove to remove you from my borders." Similar to what the Psalmist said: "They have plotted to hide snares: they said, 'Who will see them?' (Psalm 63)?" When he saw, who even searched the kidneys and hearts of the plotters, God (Jer. 17). For he said, "I have separated the peoples of the nations who would believe and obey me in various parts of the world; to whom, I beseech you, if you have anything at hand of perfect work, use it as an example for conversion, or the food of the sacred law, which shines forth in the five books written by Moses, or whatever you can find from yourselves, diligently offer it for their salvation." Some boast either of the impunity of their lie or of the denigration of Scripture, claiming that David did not hesitate to seek his and his followers' salvation by lying. They should be answered that David himself elsewhere and many of the saints often offended God by sinning, indeed no living being is justified before Him, as the great apostle said, who deserved to recline in the bosom of his Creator and Lord due to his exceptional love: "If we say that we have no sin, we deceive ourselves, and the truth is not in us" (1 John 1). However, the words of Holy Scripture were not given to us so that we might learn to sin by the examples of good people; but their sins were included in the sacred Scriptures so that we might be taught not to presume upon our own righteousness from their faults, but to trust in obtaining pardon for our own sins by their penance. Nevertheless, I believe it can be easily defended in this passage that the blessed David did not lie, but, given the necessity, concealed the truth in more cautious words. For he did not say the king was his friend, nor denied fleeing the king's plots; but he said, "The king has commanded me a certain matter, and said: Let no one know the matter about which you are…