Talmud - Beitza 17b ביצה י״ז ב׳

And if it is so that if one baked without having placed an eiruv for the joining of cooked foods, it is permitted to eat the bread, let the baraita simply teach: With regard to one who transgressed the prohibition and baked, it is permitted to eat the bread. Rav Adda bar Mattana said: There is no proof from here, as the tanna is teaching a remedy involving acting in a permitted manner, and is not teaching a remedy involving a prohibited act. The tanna did not want to teach that it is also possible to solve the problem in this proscribed manner.

The Gemara suggests: Come and hear a resolution from a different baraita: One who prepared an eiruv for the joining of cooked foods on a Festival eve may bake and cook and insulate food on the Festival for Shabbat that occurs on the following day, and if he wants to eat his eiruv on Shabbat, he has permission to do so. But if he ate it on the Festival before he baked or before he insulated, he may neither bake, nor cook, nor insulate, neither for himself nor for others, and likewise others may neither bake nor cook for him.

However, even without an eiruv, one in this situation may cook for the Festival itself, and if he left over part of what he cooked, he has left it over for Shabbat, provided that he does not employ artifice to circumvent the prohibition by saying that he is cooking a large amount for guests on the Festival, when in fact he has Shabbat in mind. And if he employed artifice to circumvent the prohibition, it is prohibited to eat the food, by decree of the Sages. This indicates that one who cooks on a Festival for Shabbat in a prohibited manner may not eat the food.

Rav Ashi said: This is no proof, as you speak of a case of artifice, and a case of artifice is different, as the Sages were more stringent with regard to one who employs artifice than with regard to one who intentionally cooks on a Festival for Shabbat. One who purposely transgresses is aware of his sin; therefore, he might repent and desist from his prohibited behavior, thereby preventing others from learning from his actions. However, one who employs artifice to circumvent a prohibition thinks that he is acting in a permitted manner. He is therefore likely to continue his practice. Furthermore, people might emulate him, and the halakha of preparing an eiruv might be forgotten.

Rav Naḥman bar Yitzḥak said that there is another reason to reject the proof from this baraita: In accordance with whose opinion is this baraita? It is in accordance with the opinion of Ḥananya and in accordance with the opinion of Beit Shammai. As it is taught in a baraita that Ḥananya says that Beit Shammai say: One may not bake bread on a Festival for Shabbat unless he prepared an eiruv for the joining of cooked foods on the eve of the Festival specifically with bread; and one may not cook any type of dish unless he prepared an eiruv with a cooked dish; and one may not insulate food unless there was hot food insulated from the eve of the Festival.

And Beit Hillel say: One may prepare an eiruv for the joining of cooked foods with one cooked dish and use it for all his needs, i.e., baking, cooking, and insulating. Since Ḥananya’s opinion in accordance with the opinion of Beit Shammai is strict in this case, it may be assumed that he is stringent after the fact as well, and therefore the baraita provides no proof.

The Gemara offers yet another suggestion. We learned in a mishna: In the case of one who transgressed a rabbinic prohibition and tithed his produce on Shabbat, if he did so unwittingly, he may eat of it; if he acted intentionally, he may not eat of it. This indicates that one may not derive benefit from a transgression that he committed intentionally. The Gemara rejects this argument: No, it is necessary to teach this halakha with regard to a case where he has other produce and therefore does not greatly suffer as a result. However, the Sages may have been more lenient with one who did not make an eiruv for the joining of cooked food and consequently has nothing to eat.

The Gemara poses another resolution: Come and hear a proof from a different source: In the case of one who immerses his vessels on Shabbat, an activity that the Sages prohibited because it is akin to repairing a vessel, if he did so unwittingly, he may use them; however, if he did so intentionally, he may not use them. This shows that the product of an action performed in a prohibited manner is prohibited.

The Gemara rejects this argument: No, it is necessary to teach this halakha with regard to a case where he has other vessels and is not forced to use these ones. Alternatively, it is possible for him to manage by borrowing vessels from others. But if one failed to set aside an eiruv for the joining of cooked foods, perhaps the Sages allowed him to eat the food he cooked on the Festival for Shabbat since it is difficult to obtain food from others on Shabbat.

The Gemara suggests another proof: Come and hear that which was taught in the following baraita: In the case of one who cooks on Shabbat, if he did so unwittingly, he may eat the food that he cooked; but if he cooked it intentionally, he may not eat it. This demonstrates that one who purposely violated a prohibition may not benefit from his prohibited action. The Gemara rejects this argument: There is no proof from here; the prohibition of Shabbat desecration is different, since it entails karet and execution by a court. The same stringency might not necessarily apply to cooking on a Festival for the sake of the next day, and therefore the question raised above remains unresolved.

§ It is stated in the mishna: Beit Shammai say that for the purpose of the joining of cooked foods one must prepare two cooked dishes, whereas Beit Hillel say that one dish suffices. The Gemara comments: The mishna is not in accordance with the opinion of this tanna, who taught in the Tosefta that Rabbi Shimon ben Elazar said: Beit Shammai and Beit Hillel agree that two dishes are necessary. With regard to what do they disagree? They disagree with regard to a fried fish and the egg on it, as Beit Shammai say: Two proper dishes are required, and this fish is considered only a single dish; and Beit Hillel say: One dish of this kind is viewed as two dishes and is therefore suitable for an eiruv for the joining of cooked foods. And they both agree that if one sliced a cooked egg and placed it inside the fish, or if he mashed leeks [kaflotot] and placed them inside the fish, they are considered two dishes.

Rava said: The halakha is in accordance with the opinion of the tanna of our mishna and in accordance with the opinion of Beit Hillel that one dish suffices.

The mishna states that if one ate the food prepared before the Festival as an eiruv or if it was lost, he may not rely on it and cook with the initial intent to cook for Shabbat. Abaye said: We have a tradition that if one prepared a proper eiruv and began kneading his dough on a Festival for Shabbat, and in the meantime his eiruv was eaten, he may finish baking the bread. Since he had begun in a permitted manner, he is allowed to complete the process and bake the bread.

MISHNA: If a Festival occurs directly after Shabbat, i.e., on a Sunday, and one wishes to behave in a proper manner and purify himself and his vessels in honor of the Festival, Beit Shammai say: One must immerse everything before Shabbat, and Beit Hillel say: Vessels must be immersed before Shabbat, but a person may immerse himself even on Shabbat.

And Beit Shammai and Beit Hillel both agree that one may bring ritually impure water into contact with ritually pure water in stone vessels on Shabbat in order to purify the water. Impure water can be purified if it is placed into a vessel that does not contract ritual impurity, such as a stone vessel, and then lowered with the vessel into a ritual bath. The water becomes purified when it comes into contact with the water of the ritual bath. Although this is not considered proper immersion, water may nevertheless be purified in this manner. However, one may not immerse the impure water in a ritually impure vessel in order to purify the vessel at the same time. Likewise, one may immerse on a Festival from one principle to another, and from one group to another, as will be explained in the Gemara.

GEMARA: In any event, everyone agrees, i.e., both Beit Shammai and Beit Hillel agree, that one may not immerse a vessel on Shabbat. The Gemara asks: What is the reason that one may not do so? Which type of prohibited labor does it involve? Rabba said: It is a decree issued by the Sages as a preventive measure,

Traduction : The William Davidson digital edition of the Koren Noé Talmud, with commentary by Rabbi Adin Even-Israel Steinsaltz.

Beitza 17b examines eiruv tavshilin rules, debating whether food prepared for Shabbat via forbidden methods or deceptive intent on a Festival remains permitted.