Cooking with Fire and with Heat

  • Rav Moshe Taragin


In memory of Rabbi Moshe ben Avraham Shraga Furst z”l

Niftar 17 Tammuz 5771.

Dedicated by his family.


Dedicated by the Wise and Etshalom families

in memory of Rabbi Aaron M. Wise,

whose yahrzeit is 21 Tammuz. Yehi zikhro barukh.



The gemara in Shabbat describes several methods of cooking food with different levels of exposure to fire. These cases include cooking with derivatives of the fire (tolodot), cooking with natural heat (chama), and employing utensils that did not have direct exposure to the fire (kli sheni). In this shiur, we will explore the nature of these variations of bishul.

The mishna (38b) asserts the primary distinction between cooking with a fire and cooking with the heat of the sun. The former scenario entails the classic form of cooking and is forbidden, while the latter case is permitted. Rashi (39a) comments that cooking in the sun is unnatural and therefore permitted. This approach is difficult, since cooking with items that have absorbed heat or toldot is also uncommon, but that is nevertheless prohibited. Furthermore, this approach would impose a prohibition on any type of cooking that has become accepted. In fact, R. Moshe Feinstein (Iggerot Moshe, Orach Chaim 3:45) prohibits cooking with a microwave because it was (at the time the response was published) in the process of becoming a normal form of cooking.

A slightly different approach would assert that cooking in the sun is not focused enough to be forbidden. The heat generated by the sun is not a human instrument; it pervades our entire planet in more intense or less intense "dosages.” Positioning food in the sun therefore is not a targeted act of cooking. In contrast, placing food near an item that absorbed heat (toldot ha-or) is focused enough and specific enough to constitute a violation. According to this approach, focused cooking in sunlight might, in fact, be forbidden. Indeed, some forbid cooking while using a magnifying glass to augment the intensity of sunlight.

It is possible that one Tanna agreed with this view that cooking in sunlight is permitted because it is not a targeted act. R. Yossi claimed that cooking with the heated water near Teveria would be forbidden, similar to cooking with a fire derivative. The gemara's language suggests that he viewed these waters as being heated by the fires of gehennom. Accordingly, the prohibition would be a standard application of toldot ha'or; cooking with derivatives of fire which is forbidden. A less literal reading might assert that unlike cooking in sunlight, employing the heat of underground springs is a targeted act of cooking. One is not merely placing food in all-pervading sunlight, but rather selecting a particular area with intense heat and employing that heat for cooking. If this less literal reading of R. Yossi is correct, he would forbid cooking with any underground stream, not only the heated waters of Teveria.

A third approach to distinguish between sunlight and fire suggests that only use of actual fire can be considered a human-authored act of cooking. Placing foodstuffs in intense heat generated by the sun is not a human controlled process of cooking. The process is advanced by a natural force, not by human manipulation. The essence of the melakhot on Shabbat is human manufacture. Thus, a person violates the process of bishul only by harnessing the heat of fire, since fire is a medium that humans control. Cooking with this medium is therefore considered a human-authored activity. Although the fire continues burning without human assistance, its continued burning (allowed by the human decision of non-intervention) is considered a continuation of the human activity of lighting the fire.

A well-known gemara in Bava Kama (22a) questions the nature of culpability for damages which occur as a result of arson. According to R. Yochanan, "isho mishum chitzo" – a fire is comparable to an arrow that was shot by a person. Even though the fire appears to have an independent momentum and autonomous process, it is viewed as a continuation of human activity. Accordingly, only cooking through fire is considered a human authored infraction of Shabbat.

If this is true, perhaps only direct cooking with fire is fundamentally forbidden, while cooking with any derivative of fire may only be secondarily forbidden. This position emerges from an interesting Yerushalmi. The mishna in Shabbat (38b) prohibits cooking items in a kli rishon, an item that was directly heated on the fire. However, the Yerushalmi (Shabbat 3:4) limits this prohibition only to situations in which the fire continues to heat the kli rishon during the actual cooking process. It appears from the Yerushalmi that if the kli rishon were first removed from the fire and subsequently employed to cook, no Biblical violation would entail (although it would still be forbidden as a gezeira). The Ramban in Avoda Zara (74) claims that the Bavli agrees with this severe limitation, applying the core Biblical violation only to situations in which the fire directly advances the cooking. This position clearly emphasizes that only use of fire (as opposed to absorbed heat) constitutes a violation of bishul.

Most Rishonim disagree, however, and claim that the Bavli equates cooking in a kli rishon with cooking in the actual fire. However, even if cooking with a kli rishon is fundamentally forbidden, it may be different from other derivatives of fire, since it was directly exposed to the fire. What about fire derivatives that were not directly exposed? Perhaps the insistence upon actual fire for bishul violation would render these forms of cooking inferior, and possibly permissible.

The gemara is clear that as opposed to cooking in sunlight, - which is permitted - it is forbidden to cook with toldot ha-or – items that were exposed to the heat of fire and absorbed that heat without direct contact with the fire, such as a kettle that absorbed heat through proximity, but not direct contact. However, the nature and degree of this prohibition is not entirely clear. The Rambam appears to equate cooking with actual fire and cooking with absorbed heat, while the Yere'im appears to classify cooking with absorbed heat as merely a tolada. Furthermore, the Ritva claims that recooking certain foods, while Biblically permitted, is Rabbinically forbidden because it resembles the prohibited forms of cooking. However, recooking with secondary absorbed heat is Rabbinically permitted since it does not resemble cooking. Evidently, the Ritva maintained that cooking through contact with fire and cooking with absorbed heat are not equivalent, even though they are each forbidden.

This possible difference between cooking through direct contact with fire and cooking with absorbed heat may explain a fascinating discrepancy between cooking and baking. As noted in an earlier shiur, an intriguing Yerushalmi suggests that baking may be considered only a tolada, rather than on par with cooking, the primary av. This difference might be attributed to the difference between cooking directly on or with fire as opposed to the baking process, in which the fire heats an enclosed oven, thereby creating heat, which in turns bakes the food.

Even if cooking with heat (or baking) is completely equivalent to cooking with fire, perhaps a situation of active reduction of that heat would not be forbidden. Heat is naturally entropic and gradually dissipates. Nevertheless, it may still be viewed as a human instrument in the same manner as fire when it is applied to foods in their preparatory process. If, however, active measures to reduce this heat are performed, the heat is no longer being wielded as a human instrument for cooking.

This may explain the permissibility of cooking in a kli sheini. Tosafot (Shabbat 42b) question this allowance and conclude that the walls of a kli sheini are not heated; even though the liquid of a kli sheini is hot enough to cook inserted items, no formal bishul has taken place. Perhaps Tosafot allude to the above concept. Cooking with fire contact and with absorbed heat are both viewed as human authored cooking, and are prohibited on Shabbat. However, by actively introducing the absorbed heat into an environment that reduces that heat, one is not applying heat to cooking and no violation exists.

To summarize: The centrality of fire for bishul is to create a human authored activity. Utilizing heat alone, without fire, may not be equivalent, thereby affecting the status of kli rishon, toldot ha-or, and possibly baking. Even if utilizing absorbed heat is equivalent, actively reducing the heat would not constitute a human employment of that heat, and would therefore not violate the prohibition of bishul.

Additionally, the centrality of fire per se to bishul may lower the status of baking to a tolada, while it limits kli rishon to scenarios in which the fire was lit during the entire process.