| Chulin
One would not normally associate the prohibition to eat the gid hanashe, the sciatic nerve, with issues of business ethics. But related they are.
The Mishna teaches that “One may send the thigh [of an animal] to an idol worshipper [even though] it contains the gid hanasheh, because one can recognize its place” (Chulin 93b). The Gemara immediately notes one can only send a whole thigh to the non-Jew. However, if the thigh was cut up, making the gid hanasheh unrecognizable, one would not be permitted to send it to the non-Jew.
The Gemara offers two possible explanations for the distinction between a whole thigh and one that is cut up. The first, not surprisingly, understands this in the context of the laws of kashrut. If the thigh is chopped up, we must be concerned lest the non-Jew sell the meat to a Jew without mentioning that the gid hanasheh is hidden in the meat. The Jew, having no way to identify the gid hanasheh, would accidentally eat it, thus making the first Jew guilty of aiding and abetting[1] in the consumption of non-kosher meat by a fellow Jew.
However, if the meat is whole, the gid hanasheh would be most noticeable and thus, there is no reason to fear the Jewish consumer might come to eat it accidently.
The Gemara follows with a second explanation: namely, that sending chopped-up meat containing the gid hanasheh is a violation of the prohibition of genevat da’at, literally “stealing one’s mind”, and follows the approach of Shmuel, who said, “It is forbidden to deceive the minds of people, even that of an idol worshipper[2]”. As Rashi (Chulin 94a s.v. mishum) explains, the idolater will think that by sending him meat with the gid hanasheh removed the Jew “loves him very much”. And for good reason.
Removing the gid hanasheh is so difficult that we do not even bother to do so today, leaving that part of the animal for non-Jews. To have done so and then gift it to a non-Jew is a great display of friendship; one could argue it reflects ahavat chinam, love for no reason, as there is no logical reason to remove the gid hanasheh for the idolater.
Yet in reality, the Jew did nothing of the sort, and the Jew will be the recipient of undeserved goodwill. Whether geneivat da’at falls under the rubric of theft or lying (or both) is a subject of debate amongst the commentaries, but ultimately matters little; it is forbidden.
It is due to the difficulty in removing the gid hanasheh that Rabbi Meir rules that butchers are not believed if they claim that they have removed the gid hanasheh from the meat. While the Sages disagree, the Gemara explains that is only because they held a more lenient view in regards to how much of the gid hanasheh must be removed. But even the Sages would agree that if removing the gid hanasheh would be onerous, we would not believe the word of the butcher. That a “kosher” butcher (or anyone else) might lie if the payoff is big enough was a given to our Sages—and nothing has changed in the past 2,000 years. It is for this very reason that common practice today is to insist that a “kosher butcher” (and pretty much all food establishments) have a mashgiach, regardless of their presumed religiousity.
The Mishna could have taught the prohibition of geneivat da’at through a case involving two Jews, but instead wanted to emphasize that we dare not deceive even an idolater. In need not be said that in addition to the sin of theft and/or lying, by deceiving a non-Jew, one risks creating a chillul Hashem.
Just a few lines later, we have a Tannaitic teaching dating from years before Shmuel that states that one may not sell neveilot utreifot, unkosher meat, to an idolater (unless he notifies him that it is not kosher), both because he many sell it to another Jew and because the non-Jew may mistakenly believe that the meat is kosher and hence of higher quality. Thus, there is little need for Shmuel to repeat this same law regarding gid hanasheh. The Ritva notes that our Mishna is not discussing selling, but giving a gift to an idolater. Shmuel teaches that even when giving a gift, one can be guilty of geneivat daat. One is not allowed to create a more favourable image of oneself in any and all circumstances.
And this, despite the fact that arguably, the highest imperative of the Torah is the duty to eradicate idolatry and proclaim the oneness of G-d instead. It is not by accident that many Jews went to their deaths with the words of the shema on their lips. The lengths to which one must go to distance ourselves from idolatry is a long one. It includes not doing business with them around their holiday time, not drinking wine they touched, the prohibition of copying any of their rituals, even having similar hairstyles.
Yet we must distinguish between idolatry and idolaters. Not only may we not cheat them, we must perform acts of chesed towards them. “One sustains poor idolaters along with poor Jews, and one visits sick idolaters along with sick Jews, and one buries dead idolaters along with dead Jews” (Gittin 61a).
And when we do so, the idolaters will feel that we “love them very much”, thereby promoting harmonious relations despite deep differences.
In addition to the inherent wrong in cheating others, there is the impact such behaviour has on its perpetrators. As actions mold character, every lie, deception, obfuscation or instance of double talk takes its moral toll. This is true even in those rare circumstances when one is allowed to deceive others, such as by a permissible lie. Thus, one may do so only occasionally, lest the accumulation of permissible lies take too great a toll on one’s character.
[1] It is unlikely that this would be a technical violation of the Biblical prohibition of aiding and abetting sinners, a subset of the exhortation not to place “a stumbling block before the [morally] blind”. Such requires a direct and indispensable link between one's help and the violation of the law. This would be the case if one personally give the gid hanasheh to a Jew to eat who, absent the help, would be unable to procure the gid hanasheh. Giving it a non-Jew, who then may or may not sell it to a Jew without warning him of the gid hanasheh, does not meet such criteria. Nonetheless, we are enjoined from participating even indirectly in improper activities and hence, the Mishna’s ruling.
[2] I find it interesting that it is Shmuel who teaches that geneivat da’at of a non-Jew, an idolater no less, is prohibited. It was Shmuel who formulated the law of dina demalchuta dina, that the law of the land is the law that must be observed by all. Whether this is significant, I do not know. But what is clear is that we must ensure that our moral behaviour towards a non-Jew is at least as it is towards our fellow Jew.