Leviticus 19:11

You will not steal or lie or slander your neighbor. The precept of theft appeared in the Decalogue (Cf Ex 20,14). As for what follows: You will not lie or slander your neighbor, it would be strange if you did not lock yourself in that precept that appears there: You will not say false testimony against your neighbor (Ex 20,16), because there can not be a slander without a lie, something that contains in the general statement about the false testimony. But there is a serious problem about whether these things can be admitted in any case. With regard to the lie, as it seems to almost everyone that a lie can be said to save one when no one is harmed, is it possible to affirm the same about theft? Can a theft be committed when no one is harmed? On the contrary, it can be done even when one looks at the one who is being robbed, as is the case when one steals the sword of a man who wants to kill himself. Actually, the slander I do not know if one could be made to his advantage. When Joseph slandered his brothers about the glass and charged them with the false accusation that they were spies, perhaps he did it to achieve greater joy, which they would later enjoy. Although if we tried to determine these things with appropriate definitions, perhaps there is no theft more than when harm is done to others, hiding what is foreign. And there is no slander more than when harm is done to others, accusing them of false guilt. But we can not say that lie exists only when harm is caused to our neighbor. When one says a false thing knowingly, it is certainly a lie, whether it is harmed with it or if no harm is done to anyone. Therefore, the serious problem about lying, that is, if the lie could ever be lawful, would probably be solved easily if we contemplated only the commandments, and not the examples. Because what is more blunt than this commandment: You will not lie? It is stated as: You will not make idols-which can never be lawful-and also what the Scripture says: You will not commit adultery-who would dare to say that adultery could ever be lawful? And the same as: You will not steal - according to that definition of theft the theft can never be lawful. And: You will not kill (Ex 20,4.13.14.15), because when a man is lawfully killed, the law kills him, not you. Can it be said that when a man lies lawfully, does the law lie? The examples make the question very…