LEV375 The Rabbis also root the prohibition against intentionally giving bad advice in another Torah Law: [this verse]. Jewish tradition understands this as not only outlawing playing a cruel trick on a blind person, but also as taking advantage of one who is "blind" to the matter at hand. Thus, anyone who takes advantage of another's ignorance and gives that person inappropriate advice is regarded as having violated this biblical law (It applies as well to one who takes advantage of another's addiction or lack of self-control. Thus, providing liquor to an alcoholic is a violation of this law.) A rabbinic commentary explains: "If a man seeks your advice, do not give him counsel that is wrong for him. Do not say to him, 'Leave early in the morning,' so that thugs might mug him. Do not say to him, 'Leave at noon,' so that he might faint from heat. Do not say to him, 'Sell your field and buy a donkey,' so that you may circumvent him, and take the field away from him" (Sifra, Leviticus 19:14). As the first examples make clear, don't play cruel practical jokes on people, and as the last example teaches, if you have a personal interest in the matter, you must disclose it.
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