Introduction to Bishul by Rabbi Chaim Jachter



This week we begin a series of essays that will discuss the topic of Bishul, the prohibition to cook on Shabbat.  In this essay, we will outline some of the basic concepts regarding Bishul, which are essential for comprehending this vitally important topic.  One should note that a comprehensive treatment of this topic appears in the second volume of Rav Shimon Eider’s Halachos of Shabbos.  It is an excellent resource for one who wishes to delve deeply into this subject. 

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 is especially true in the context of the laws of Bishul.  We will begin our review of basic concepts by outlining those principles that are directly relevant to prohibited activities on a Torah level. 

Yad Soledet Bo

One does not violate the prohibition of cooking a liquid unless one heats the liquid to the point that it is hot to the touch (Yad Soledet Bo, see Shabbat 40b).  The Talmudic term Yad Soledet Bo may be translated as “the hand recoils from it.”  Rabbis for the past century have debated over the exact temperature at which we consider an item to be Yad Soledet Bo.  Rav Moshe Feinstein (Teshuvot Igrot Moshe Orach Chaim 4:74:Bishul:3) writes that the minimum temperature of Yad Soledet Bo is 110°F.  Rav Shlomo Zalman Auerbach (Teshuvot Minchat Shlomo 1:91:8) seeks to demonstrate in a very creative way that it cannot be less than 113°.  Rav Aharon Kotler (cited by Rav Shimon Eider, Halachos of Shabbos 2:243 note 19) asserts that Yad Soledet Bo is not less than 120°.  Interestingly, the Darkei Teshuva (105:51) cites that the traditional practice of Halachic authorities to determine if something is Yad Soledet Bo is simply to put a finger in it aמd see if your hand recoils.

This author’s experience at Yeshiva University might shed light on the divergence of opinions regarding the exact temperature of Yad Soledet Bo.  One of the YU Rabbeim

brought a group of students to one of the college’s laboratories and displayed cups filled with water.  The cups were heated to a variety of temperatures ranging from 110° to 120°.  Some of the students felt that 110° was hot to the touch and others felt that only 120° was hot to the touch.

Maachal Ben Drosai

A bandit known as Ben Drosai, who lived during the time of the Gemara, was constantly fleeing 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 Maachal 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 Maachal Ben Drosai.  The Rambam (Hilchot Shabbat 9:5) believes that it refers to food that is half cooked.  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.

Ein Bishul Achar Bishul

One does not violate a Torah prohibition if he reheats 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 was baked, or roasting an item that was cooked.  We will, Iy”h, discuss this topic at length in a subsequent issue.

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.  The opinion of Tosafot is accepted as normative (Mishna Berura 318:35).

There is substantial debate about the parameters of the rules pertaining to Bishul in a Kli Sheni.  Many argue that items that are easily cooked (Kalei Habishul) can cook 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 if even Kalei Habishul may be cooked in a Kli Shlishi.  We plan to discuss these issues in much greater detail in a later issue. 


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 Hagasa of even a fully cooked item constitutes a Torah level prohibition.  Halachic authorities seriously consider this surprising opinion of the Kol Bo (see Shulchan Aruch 318:18 and commentaries ad. loc.). 

Rabbinical Prohibitions

Chazal added numerous prohibitions to the Halachot concerning Bishul.  In later issues, we hope to examine at some length the issues of Shehiya, Hachazarah, and Hatmana.  We will now briefly define these terms.


Chazal forbade us to leave food cooking on the fire as Shabbat is about to begin (Shehiya).  Chazal were concerned lest the individual stir the coals in order to hasten the cooking process (Shema Yechateh Bagechalim, see Shabbat 18b).  The Chachamim and Chanania (ibid.) vigorously debate whether this prohibition applies to food until the point that it is fully cooked and its taste cannot be improved (Mitztamek V’rah Lo) or only until it reaches Maachal Ben Drosai.  In addition, we should note that 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 the beginning of Shabbat (Kedeira Chaita, Shabbat 18b). 


Chazal forbade us from returning even fully cooked food to the fire on Shabbat (Hachazara).  Rishonim debate whether Chazal forbade Hachazara due to concern lest one come to stir the coals or because Hachazara has the appearance of cooking (Meichzi K’mevashel).  Rishonim and Acharonim debate about permissible ways to reheat food on Shabbat, such as placing the food on top of a pot on the fire that contains food (Kedeira Al Gabei Kedeira).


Chazal forbade enveloping food on Shabbat due to concern that one might come to stir the coals (Hatmana).  Chazal even forbade Hatmana before Shabbat if one envelops the food in a material that adds heat to the food (Davar Hamosif Hevel).  Today, a major controversy rages whether the use of a two-piece crock-pot constitutes Hatmana. 


There are numerous disputed areas regarding the laws of Bishul.  In the next few issues, we will explore these areas in more depth, and we will begin to understand the variety of practices in this area of Halacha.

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