Last week's issue discussed the biblical prohibition against warming food on Shabbat. This week's issue will discuss the rabbinic prohibitions that relate to warming food on Shabbat. There are two basic rabbinic concerns relating to warming food on Shabbat. The first is the concern that certain situations may lead one to instinctively raise the temperature of the fire. The second is a concern that certain situations may give off the impression that one is cooking rather than warming.

Shema Yechateh B'Gechalim: The Concern for Raising the Temperature
In Talmudic times, ovens and stoves were fueled by coals. The Gemara, Shabbat 18b, states that in certain situations there is a concern that one may instinctively stoke the coals in order to expedite the cooking or warming process. The Gemara, Shabbat 36b, applies this concern to two specific situations.

The first situation is one where someone began cooking food before Shabbat and the process is going to finish on Shabbat. The concern is that one may become anxious that the food is not going to be complete in time for the meal and stoke the coals in order to ensure that the food will be ready. There is a dispute among the Tannaim regarding the extent of the prohibition. According to Chananiah, this concern only applies if the food has not yet reached ma'achal ben derosai (minimally edible; this concept was discussed in last week's issue). According to Rabanan (the rabbis who disagree with Chananiah), this concern applies in any situation where the quality of food will benefit from heat. Even if the food is fully cooked but the food will benefit from the evaporation of some its moisture (mitztamek v'yafeh lo) there is a concern that someone may stoke the coals.

Rif, Shabbat 16a, and Rambam 3:4, rule in accordance with the opinion of Rabanan. Rashi, Shabbat 37b, s.v. V'Rav Sheshet, and Tosafot 18b, s.v. Bashil, rule in accordance with the opinion of Chananiah. Shulchan Aruch Orach Chaim 253:1, presents both opinions but seems to side with the opinion of Rabanan. Rama, ad loc., sides with the opinion of Chananiah. Nevertheless, Mishna Berurah, Biur Halacha s.v. V'Nahagu, states that ideally one should follow the opinion of Rabanan.

The second situation involves placing food onto the fire on Shabbat. The Gemara, Shabbat 36b, states that both Rabanan and Chananiah agree that one may not place food onto the stove on Shabbat unless the concern of shema yechateh b'gechalim is mitigated. [This explanation follows the opinion of Rabbeinu Tam, Sefer HaYashar, Chiddushim no 191. According to Ran, Shabbat 15b, s.v. Gemara, the reason why one must cover the ashes in order to place something on the fire on Shabbat is that there is a concern of mechzi k'mevashel (which will be discussed in the next section). Mishna Berurah, Sha'ar HaTziun 253:37, quotes both opinions.]

The Mishna, Shabbat 36a, provides a solution to the concern of shema yechateh b'gechalim. The Mishna states that it if one removes the coals from the oven or one covers the coals with ashes, there is no concern of shema yechateh b'gechalim (unless the food is in a baker's furnace, see Rabbeinu Chananel, Shabbat 38b). Rambam, Hilchot Shabbat 3:4, explains that the reason why covering the coals with ashes alleviates the concern of shema yechateh b'gechalim is that when one covers the ashes, he has performed an act symbolizing that he is not interested in tampering with the coals.

R. Shimshon Ben Tzadok, Tashbetz Katan no. 27, introduces the concept of placing a sheet of metal or wood on top of a stove in order to permit placing food on top of the sheet. Magen Avraham 253:31, states that placing a sheet on top of the stove is the equivalent of covering the ashes. Mishna Berurah 253:81, codifies Magen Avraham's statement. R. Moshe Feinstein, Igrot Moshe, Orach Chaim 1:93, notes that in modern-day stoves, the only option of avoiding the concern of shema yechateh b'gechalim is by placing a sheet of metal (commonly known as a blech) on the stove. R. Feinstein adds that ideally one should also cover the knobs that control the heat.

Mechzi K'Mevashel: It Appears as if One is Cooking
The Gemara, Shabbat 38b, states that it is permissible to remove a food item from the fire and replace it on Shabbat if upon removing the food he has in mind to return the food to the fire and the food remains in his hand the entire time. If he places the food on the floor, he may not return the food to the fire. [The Gemara questions the case of someone who allowed the food to leave his hand but did not place the food on the floor. Rama, Orach Chaim 253:2, rules that it must remain in his hand.] Ran, Shabbat 17b, s.v. Lo Shanu, explains that the necessity for these conditions is to avoid the concern that it appears if as one is cooking on Shabbat (mechzi k'mevashel). If upon removing the food, one has in mind to replace it and the food remains in one's hand, the replacing of the food is considered a continuation of the original state and there is no concern for mechzi k'mevashel.

Mishna Berurah, Biur Halacha 253:2, s.v. V'Da'ato, rules that although ideally one should have in mind to return the food to the fire and that one should ensure that the food remains in his hand, in a case of necessity, one may be lenient if only one of those conditions was fulfilled. R. Moshe Feinstein, Igrot Moshe, Orach Chaim 2:69, states that one may certainly be lenient in this situation if the food was on the fire on Shabbat.

Rashba, Shabbat 40b, s.v. Maivi, presents another solution to avoid the problem of mechzi k'mevashel. Rashba states that it is permissible to place a (cold) fully cooked food on top of a dish that is already on the fire. His rationale is that this is not the normal way to cook an item (therefore there is no concern of mechzi k'mevashel). P'ri Megadim, Eshel Avraham 253:33, rules that the bottom utensil must contain food. However, Machatzit HaShekel 253:34, rules that even if there is no food in the bottom utensil, one may place food on that utensil. Mishna Berurah, Biur Halacha 253:3, s.v. V'Yizaher, cites the opinion of P'ri Megadim.

Summary and Practical Applications
There are three basic concerns that must be mitigated in order to allow one to warm food on Shabbat. The first concern is the biblical prohibition against cooking. This was the subject of last week's issue and the basic conclusion was that fully cooked solid foods are generally not subject to the prohibition against cooking, while liquid foods are subject to the prohibition against cooking if they have cooled off. The second concern of shema yechateh b'gechalim can be mitigated if one covers the fire. The third concern of mechzi k'mevashel can be mitigated if one is merely "returning" the food to the fire (following the conditions addressed previously), or one places the food on top of a dish that is already on the fire.

There are modern day appliances that may mitigate some of these concerns in a different manner. R. Tzvi P. Frank, Orach Chaim 1:136, rules that an appliance whose temperature is not adjustable (e.g. a hot-plate) is not subject to the concern of shema yechateh b'gechalim. Some Acharonim rule the concern for mechzi k'mevashel is mitigated if the appliance is used for warming and not for cooking. [see R. Ovadiah Yosef, Yabia Omer 7:42:10, R. Moshe Feinstein, Igrot Moshe Orach Chaim 4:74:35, R. Shimon Eider, Hilchot Shabbat, IV, note 566 and R. Mordechai Willig, Am Mordechai, Shabbat 7:2]. One application of this ruling is that one may place a fully cooked item onto a non-adjustable hot-plate on Shabbat. [See Am Mordechai, ibid and R. Yehoshua Y. Neuwirth's approbation to Am Mordechai. According to R. Neuwirth, in Israel it is prohibited because there are people in Israel who use the hot-plate for actual cooking and therefore, the prohibition of mechzi k'mevashel is not mitigated.]