Defining Prohibited Bishul (Cooking on Shabbat) (I)

The mishna lists “ha-ofeh,” baking, as one of the 39 forbidden melakhot on Shabbat, and the gemara (Shabbat 74b) describes the inclusion of baking as opposed to cooking as purely stylistic. Indeed, cooking, and not baking, was performed in the construction of the Mishkan, which serves as the template for forbidden activities on Shabbat. However, in as much as the mishna describes the process of bread baking, the act of baking, and not the act of cooking, was employed to represent this act. This series of shiurim will explore the nature of the prohibition to cook on Shabbat. Ultimately, the question regarding the nature of bishul may help determine whether baking and cooking are identical.

The first issue surrounds the source of heat. The mishna (38b) cites a debate about baking with products heated by sunlight (for example, a kerchief that has absorbed solar energy). R. Yossi allows this method of cooking, whereas the Chakhamim prohibit it. Ultimately, the gemara claims that everyone allows cooking in the actual sunlight, while everyone prohibits cooking with items that have absorbed energy generated by fire (toldot ha-or).

The gemara does not clarify the reason for the universal permissibility of actual sunlight cooking. Theoretically, if solar energy could generate requisite cooking heat levels, we would logically conclude that the process should be forbidden. Rashi explains that this is not the classic “derekh” of bishul, the method through which cooking is usually accomplished, and it is therefore not forbidden. Rashi does not provide any source limiting the prohibition to standard cooking procedures.

Perhaps the permissibility of sunlight cooking stems from the absence of any “action” with the source of heat. Sunlight pervades our entire living space, at least to some degree, and its heat is not subject to human control (at least, not without the use of solar panels). Placement of an item in sunlight is not an act of manipulating energy toward cooking, since every human activity occurs within space pervaded by sunlight. The absence of any action related to the “heat source” renders this non-activity permissible.

Interestingly, the Shevitat Ha-Shabbat cites those who question the permissibility of the use of a magnifying glass to intensify the heat source and thereby cook food on Shabbat. Presumably, Rashi would permit this activity, since the use of a magnifying glass is not a standard cooking procedure. However, if the permissibility stems from the absence of any distinct manipulative activity with sunlight, perhaps this distinct application of sunlight would be forbidden.

This question raises a broader question about the nature of the cooking prohibition on Shabbat. Is the melakha defined as an act of applying heat to items, or is it defined as advancing food toward digestibility through heat processing? Must there be an act performed upon fire or heat in applying it to food in order for it to be considered a violation of this issur? Or does a person violate bishul even if he does not directly perform an act with fire, as long as food has been processed through heat?

This question dramatically impacts the types of bishul that are Biblically forbidden. For example, is it Biblically forbidden to cook in a utensil that is no longer on the fire, a kli rishon she-husar me-al gavei ha-esh? The mishna in Shabbat (42a) states that it is forbidden, but the gemara does not clarify if the issur is de-oraita or de-rabbanan. The Yeurshalmi (3:4) cites one opinion that ranks the issur as Rabbinic, and the Ramban in Avoda Zara appears to adopt this principle. Although the heat potency of this removed pot may be the same as that of pots still on the fire, there is clearly a difference between the human manipulation of the actual fire and its application to food. When cooking directly upon a fire, a person is directly applying fire-generated heat to cook the food. When cooking on a removed pot, he may not be performing an act upon the fire. If bishul entails an action with fire, cooking on recently removed pots may not constitute this forbidden activity and may only be forbidden mi-derabbanan.

Even if we do not accept the Yerushalmi and the Ramban (and it appears that the Ran in Avoda Zara indeed disagrees), we might still argue that bishul entails direct application of fire. Perhaps cooking with a recently removed pot does constitute manipulation of fire, as the fire directly heated the pot which in turn transferred its heat-generated and human-applied energy to the food. But what would happen if the process occurs in less direct fashion? For example, if a person pours hot liquid from a kli rishon in which they were heated (iruy kli rishon) upon food, thereby partially cooking them - does this entail a Shabbat violation of bishul?

This issue is not directly discussed by the gemara (although it does appear to be a debate between R. Yosi and R. Yona in the Yerushalmi), and the question is debated by various Rishonim. The R”i (cited by Tosafot in Shabbat and Avoda Zara) cites a gemara in Zevachim (95b) that implies that pouring hot liquid from a kli rishon leads to transfer of taste and possible issurim in the case of non-kosher foods. If iruy kli rishon causes taste transfer, it should presumably also constitute bishul. The Ramban, however, rejects this comparison. Even if iruy enables taste transfer, it is not considered an act of cooking. Perhaps the Ri and the Ramban are debating the parameters of bishul on Shabbat. The Ri defined any food processing through heat as forbidden. If taste can be transferred when being cooked through iruy kli rishon, “cooking” in the context of Shabbat bishul occurs as well. After all, food has clearly been processed, as evidenced by the transference of forbidden taste. By contrast, the Ramban distinguishes between taste transfer and Shabbat bishul activity. Although the former can be accomplished through any heat energy, Shabbat bishul requires human application of fire upon food. Although cooking in a recently removed pot entails human application of fire (since the pot was originally placed upon the fire), cooking through the pouring of liquid does not entail “application of fire to food.” The fire created energy in a liquid, but transferring that to a secondary substance may not be direct enough to qualify as an act of cooking according to the Ramban.

It is possible that this gauge of whether humans have manipulated fire to food can explain the astonishing permissibility (at least Biblically) of cooking in a kli sheni (a pot into which food cooked in a pot on the fire was transferred). The aforementioned mishna that prohibits cooking in a kli rishon allows it (Biblically) in a kli sheni. Presumably, the heat level of a kli sheni can reach the requisite level for cooking, and yet the Torah does not prohibit this process. Tosafot (40b) address this issue and their answer supports two very different explanations. Their concluding comments assert that the walls of the second pot provide a cooling effect, and this is counterproductive to cooking and food processing. By placing food in a walled container designed to cool and whose walls prevent cooking, no violation of cooking occurs, even if other materials in this container enable cooking. However, Tosafot’s initial comments suggest that cooking in a kli sheni is permissible because its walls were never in physical contact with fire. Employing a pot that never contacted fire is not considered a manipulation of fire and cannot be considered an act of bishul.

If bishul entails an act of applying fire upon food, activities that are less direct applications of fire may not be Biblically forbidden.