The Prohibition of Bishul in Cases of Limited Change

  • Rav Moshe Taragin


In a previous shiur, we explored the nature of the ein bishul achar bishul exception. Is re-cooking permitted because it does not improve the item, or is it permitted because the process is rendered redundant by the previous cooking? This distinction crystallizes a question about the nature of the bishul prohibition itself. Is bishul prohibited because of the improvement it imparts, or is the process itself prohibited, independent of any improvement? In this shiur, we will explore potential test cases in which a cooking process has definitely occurred but typical improvement has not taken place.

Perhaps the most extreme application of this scenario relates to burning and consuming items. When heat is applied to firewood, a process similar to cooking occurs. However, the resultant item is not improved, but rather destroyed. Would such a scenario entail a prohibition of bishul?  

The gemara (Shabbat 74b) describes a bishul prohibition for someone who places a water-logged item in a fire. It is unclear whether the item in question is made of wood or metal, but presumably bishul is violated by stiffening the item in a way similar to the way food is processed through the application of heat. The Yere'im, however, claims that the prohibition occurs because of the evaporation of the water within the item. Similarly, the Mordechai (434) prohibits drying a wet towel near a fireplace because the evaporation of the water entails an issur of bishul. The comments of Tosafot Ha-Rosh in Yevamot (6a) also indicate that he viewed burning oil or wax as a possible violation of bishul.

Interestingly, it appears that this question is the subject of a debate between two Tanna’im cited in the Yerushalmi (Shabbat, perek 2).The Yerushalmi discusses the burning of korbanot parts on the mizbei’ach at night and which Shabbat violation this would theoretically entail. According to R. Yehuda, the prohibition of mav’ir, lighting a fire, has been violated, since the animal parts will increase the spread of the mizbei’ach fire. According to R. Yossi, bishul has been performed. Burning animal parts appears to be similar to evaporating water or burning oil. In each instance, the material is consumed. Nevertheless, at least according to some opinions, bishul has occurred.

Perhaps this debate reflects the nature of bishul. If bishul is defined as a process that endows improvement to a material through application of heat, it is not violated if the item is consumed by insertion in fire or exposure to heat (in the case of evaporation of water or burning of wax). The item has not undergone a process of improvement; if anything, its consumption is a “regression.” Evidently, the Rishonim who did view these scenarios as violations of bishul viewed this melakha in extremely formal terms. Bishul is defined as any process that resembles cooking and baking in that it applies heat to an item.

A related scenario of bishul would emerge regarding cooking of food that can be eaten raw, such as fruits and certain vegetables. Would such cooking be a violation of bishul? This question was the subject of an interesting machloket about cooking oil (which in ancient times was ingested “raw”). The gemara in Shabbat (40b) cites the Tanna Kamma, who claims (at least according to the understanding of R. Yosef and Rabba) that cooking oil is not forbidden. The Maggid Mishneh (Hilkhot Shabbat 9:3) assumes that bishul isn’t violated because oil can be eaten without additional processing.  Subsequently, the gemara cites R. Yehoshua, who contends that cooking oil does constitute a bishul violation.

These Tanna’im may in fact be debating the aforementioned definition of the prohibition of bishul. If the violation is defined as improving food through the processing of cooking, it is reasonable to suggest that cooking items that can be eaten raw does not constitute a bishul violation, since no major improvement has been rendered. However, if bishul is defined in a more formal manner – as the application of heat to food in a manner that alters its composition – it is more difficult to distinguish between ordinary foods and those that can be eaten raw.

Of course, the more intriguing and common instance of something that is ingested “raw” is water. The gemara explicitly states that cooking water is forbidden on Shabbat. Once again, if the prohibition of bishul is defined as a formal cooking process, the extension of the prohibition to water is quite logical. If, however, bishul entails some form of improvement, cooking water may not be similar to other forms of bishul, as cooked water has not essentially changed; it is the same water, just hotter!

Alternatively, one might argue that since heated water is vastly improved over cold water, it may nevertheless resemble standard bishul; cooking water does, in fact, entail improvement. However, it is also possible to claim that the improvement necessary to define the melakha as bishul is reconstitution of the item, which does not take place when water is cooked.

In fact, based on the incongruity between classic bishul of improvements of heating water, many Rishonim suggest that heating water is a different category of bishul than cooking and baking. One indication of this is the different criterion used to evaluate when bishul is violated in the cases of liquids and solids. Bishul is violated when water is heated to yad soledet bo, approximately 45 whereas the issur of bishul for food is gauged by the degree of cooking – namely, how much the item has been transformed. The fact that we use a different measurement for heating water – not the degree of change, but rather the degree of heating – suggests that it is not fully incorporated in the classic violation of bishul.

A second indication of a difference is the prohibition of reheating water that had previously been heated and subsequently cooled. As noted in an earlier shiur, the principle of ein bishul achar bishul typically indicates that re-cooking food is permitted. Some (although not all) Rishonim differentiate between reheating solids and reheating liquid foods. However, all of these Rishonim agree that it is prohibited to reheat water that has cooled. This confirms the fact that heating water is a different violation, which deviates from the principle of ein bishul achar bishul that governs most foods.

In summary, it appears that heating water may not be defined as classic bishul. If bishul is defined as processing food through heat, it would be easier to integrate heating water within the standard prohibition. However, if bishul is defined as improving the food, there would seem to be a different category for the prohibition of heating water.