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Introduction
Let us begin our exploration of Hilchot Bishul by outlining some basic concepts regarding Bishul (the prohibition to cook on Shabbat), which are essential for comprehending this vitally important topic. Outstanding and comprehensive treatments of this topic appear in several recently published Sefarim beginning with the second volume of Rav Shimon Eider’s Halachos of Shabbos and culminating with Rav Mordechai Willig’s incisive and thorough analysis in his “The Laws of Cooking and Warming Food on Shabbat” (supplemented by comments from Rav Hershel Schachter and Rav Yaakov Neuberger).
Torah Prohibited Activities
In general, it is essential to distinguish between activities that are prohibited on a Torah level and those only prohibited on a rabbinical level. This distinction is especially true regarding Bishul. The following are principles that are directly relevant to prohibited activities on a Torah level.
Yad Soledet Bo
Bishul does not apply to a liquid until it is hot to the touch (Yad Soledet Bo, the hand recoils from it; Shabbat 40b). The Poskim of the past century have debated the temperature of Yad Soledet Bo. In our next section, we discuss this question at some length.
Ma’achal Ben Drosai
A notorious bandit of Talmudic times, known as Ben Drosai, was constantly on the run from the authorities and had limited opportunities to cook his food. He therefore cooked his food only to the point that it was barely edible. Chazal, in turn, refer to food cooked to the point that it is marginally edible as Ma’achal Ben Drosai (the food of Ben Drosai). One who cooks solid food to the point of Maachal Ben Drosai violates the biblical prohibition of cooking on Shabbat.
The Rishonim debate at what point solid food is defined as Ma’achal Ben Drosai. The Rambam (Hilchot Shabbat 9:5) believes that it refers to half-cooked food. Rashi (Shabbat 20a s.v. Ben Drosai), on the other hand, believes that it is one-third cooked. The Shulchan Aruch (O.C. 254:2) follows the Rambam’s opinion, but the Mishna Berura (introduction to chapter 253 and 253:38) also cites Rashi’s view as authoritative. The Mishna Berura writes that one may rely on Rashi’s lenient view in case of pressing need.
The Chazon Ish (Orach Chaim 37:6) writes that we assess Ma’achal Ben Derosai based on cooking time. Others (see the Piskei Teshuvot Orach Chaim 253:1 and the Orchot Shabbat 2: footnote seven) argue that experience shows that food is not even marginally edible at half of the food’s usual cooking time. Rav Mordechai Willig told me that he assesses Ma’achal Ben Derosai simply by tasting the food to see if it is marginally edible.
Ein Bishul Achar Bishul
One does not violate a Torah prohibition by reheating a food item that was cooked completely, even if the food has completely cooled down. This rule is referred to as Ein Bishul Achar Bishul.
There are many disputes regarding the parameters of this rule. Rishonim debate whether it applies only to solid food items or even to liquids. Rishonim also debate whether it applies to cooking an item that has been baked or roasting an item that has been cooked.
Kli Rishon, Irui Kli Rishon, Kli Sheni, and Kli Shlishi
A utensil that was heated by fire, even if it is not currently on the fire, is called a Kli Rishon. It is biblically prohibited to cook in a Kli Rishon. Pouring food from a Kli Rishon is referred to as Irui Kli Rishon. One pours from a Kli Rishon into a Kli Sheni. If one pours from a Kli Sheni into another utensil, the latter utensil is referred to as a Kli Shlishi.
The Gemara teaches that, generally speaking, Bishul does not occur in a Kli Sheni. The Rishonim debate the status of Irui Kli Rishon. The Ri (cited in Tosafot 42b s.v. Aval) asserts that Irui Kli Rishon has the status of a Kli Rishon. Rashbam (cited by the aforementioned Tosafot) believes that it has the status of a Kli Sheni. Tosafot (ibid.) adopts a compromise approach – it is neither like a Kli Rishon nor like a Kli Sheni. Rather, Irui Kli Rishon cooks only the thin outer layer of the food (K’dei Klipah) onto which it is poured. Tosafot’s opinion is accepted as normative (Mishna Berura 318:35 and see The Laws of Cooking and Warming Food on Shabbat pp. 65-70).
There is substantial debate about the parameters of the rules about Bishul in a Kli Sheni. Many argue that items that are easily cooked (Kalei Habishul) can be cooked in a Kli Sheni as well as a Kli Rishon. Furthermore, Acharonim vigorously debate whether the rule that Bishul does not occur in a Kli Sheni applies only to liquids or even to solid foods (Davar Gush). Finally, there is considerable debate about whether even Kalei Habishul may be cooked in a Kli Shlishi.
Yad Nichveit Bo
The Mishna Brura (318:48) cites the Chayei Adam (Hilchot Shabbat 20:4), who introduces the idea (based on the Rambam Hilchot Ma’aserot 3:15) that all agree that a liquid that is hot as Yad Nichveit Bo can cook in a Kli Sheini. The Chazon Ish (Orach Chaim 52:19) strongly questions this unique view, noting that this idea does not appear in earlier sources, but concludes that it is difficult to be lenient regarding a potential Torah-level prohibition. Rav Moshe Feinstein (Teshuvot Igrot Moshe 4:74 Bishul 17) follows the Chayei Adam and Rav Yisrael Belsky rules that 180 degrees Fahrenheit is the equivalent of Yad Nichveit Bo.
Sephardic Jews do not follow this stringency of the Chayei Adam (Rav Ovadia Yosef, Teshuvot Yabia Omer 7: Orach Chaim 40:1 and Rav Benzion Abba Shaul, Teshuvot Ohr L’Tziyon 2:30 footnote 11).
Hagasah
Stirring food in a Kli Sheni (Hagasah) makes food cook faster and violates the biblical prohibition of cooking on Shabbat (Mishna Berura 318:114). The Kol Bo adopts the startling opinion that Hagasah is forbidden even if the food is fully cooked. Some Acharonim understand the Kol Bo as teaching that the Hagasa of even a fully cooked item constitutes a Torah-level prohibition. Halachic authorities seriously consider this surprising opinion (see Shulchan Aruch 318:18 and its commentaries).
Rabbinical Prohibitions
Chazal’s three primary Bishul prohibitions are known as Shehiya, Hachazarah, and Hatmana. Let us briefly define these terms.
Shehiya
Chazal forbade leaving food cooking on the fire as Shabbat is about to begin (Shehiya). Chazal were concerned lest the individual stir the coals to hasten the cooking process (Shema Yechateh Bagechalim, Shabbat 18b). The Chachamim and Chanania (ibid.) debate whether this prohibition applies to food until it is fully cooked and its taste cannot be improved (Mitztamek V’rah Lo) or only until it reaches Ma’achal Ben Drosai. Chazal made an exception to the prohibition of Shehiya when one adds a piece of completely raw meat to the cooking pot of food at Shabbat’s beginning (Kedeira Chayta, Shabbat 18b).
Hac1hazarah
Chazal forbade us from returning even fully cooked food to the fire on Shabbat (Hachazara). Rishonim debate whether Chazal forbade Hachazara due to concern that one might come to stir the coals or because Hachazara resembles cooking (Meichzi K’mevashel). Rishonim and Acharonim discuss permissible ways to reheat food on Shabbat (more accurately described as Hanacha, such as placing the food on top of a pot on the fire that contains food (Kedeira Al Gabei Kedeira).
Hatmana
Chazal forbade enveloping food on Shabbat (Hatmana) due to the concern that it would lead to stirring the coals. Chazal even forbade Hatmana before Shabbat if one envelops the food in a material that adds heat to the food (Davar Hamosif Hevel). Today, there is considerable debate about whether the use of a two-piece crock-pot, where the heating element encloses the pot containing the food in a shell, constitutes Hatmana.
Conclusion
There are numerous disputed areas regarding the laws of Bishul. In the next sections, we delve into these areas in greater depth and begin to understand the variety of practices within this central Halachic realm.