The Sefer Yereim contends that just as there is an admonition against onaas devarim, hurting a person with words, saying something to him that disconcerts and makes him feel bad, there is also an enjoinment against looking at someone with a bad/evil look. The way we look at someone – be it with disdain, scorn, or hatred – can and does hurt.
Onaas mamone is the prohibition against cheating someone financially. It is a surreptitious form of stealing. In truth, one only fools himself. Horav Menachem Mendel, z.l., m’Varko, said, “According to Halachah, one should not cheat another Jew. Lifnim meshuras ha’din, going beyond the letter of the law, one should not cheat/fool himself. Horav Yisrael, z.l., m’Koznitz would say it is better not to fast and fool people than to fast and fool oneself. A person must have integrity in everything he does. The Chidushei HaRim would say that a thief steals only what he needs, what he himself is lacking. One who is gonev daas, fools someone, indicates that he lacks daas, common sense, intelligence.
Last, the Kotzker Rebbe would say that whoever emits a sound that lacks integrity, that is not from his heart, is a gonev daas: The kvetch that is not real; the moan that is a put on; the shuckling – moving to and fro – during davening insincerely, performed only to call attention to oneself, is geneivas daas.
