Bisul besábát / leves melegítés

4. Food fully cooked which has cooled down may not be reheated because of the Melacha of Bishul (cooking). RAMA some hold that this is only if the food is Mitztamek ve’yafe lo. [R' Yerucham] Food not fully cooked, even if cooked to the degree of Ma’achal ben Derusa’i and even if the food is hot, is nevertheless forbidden to cook any further. The reheating that is forbidden, only applies to food with liquid, but a cooked food item that is a solid (has no liquid), may be immersed in hot water on Shabbos. A solid food item that has not been cooked before Shabbos, may not be immersed into hot water on Shabbos, but one may pour hot water over it on Shabbos, with the exception of aged salted food and a fish called “Kulias ha’ispanin”, which do not require much cooking, and by pouring water over them one completes the Melacha. RAMA: This rule applies to all hard foods that cannot be eaten without first marinating them. Therefore one may not soak them (in hot water) on Shabbos, as it is a completion of a Melacha. [Ha'gahot Mordechai]

Any salted food item that was already placed in hot water, i.e., cooked, before Shabbat, one may soak it in hot water even on Shabbat. And anything that was not placed in hot water before Shabbat, one may rinse it in hot water on Shabbat but may not soak it, with the exception of old salted fish and small salted fish and the kolyas ha’ispanin fish, for which rinsing with hot water itself is completion of the prohibited labor of cooking.

...

MISHNA:Any salted food item that was already placed in hot water, i.e., cooked, before Shabbat, one may soak it in hot water even on Shabbat. And anything that was not placed in hot water before Shabbat, one may rinse it in hot water on Shabbat but may not soak it, with the exception of old salted fish and small salted fish and the kolyas ha’ispanin fish, for which rinsing with hot water itself is completion of the prohibited labor of cooking.

Similarly, the Sages taught: One may bring a jug [kiton] full of cold water and place it opposite the bonfire on Shabbat; not so that the water will heat up, as it is prohibited to cook on Shabbat, rather to temper the cold, as one is permitted to render water less cold on Shabbat. Rabbi Yehuda says: A woman may take a cruse of oil and place it opposite the bonfire; not so the oil will cook, rather, so it will warm until it is lukewarm. Rabban Shimon ben Gamliel says: A woman may smear her hand with oil, and heat it opposite the fire, and afterward smear her young son with the heated oil, and she need not be concerned about cooking on Shabbat.

Rav Yitzḥak bar Avdimi said: One time I followed Rabbi Yehuda HaNasi into the bathhouse on Shabbat to assist him, and I sought to place a jar of oil in the bathtub for him, to heat the oil somewhat before rubbing it on him. And he said to me: Take water from the bath in a secondary vessel and place the oil into it. The Gemara remarks: Learn from this comment of Rabbi Yehuda HaNasi threehalakhot: Learn from it that oil is subject to the prohibition of cooking. This explains why he prohibited placing it in the bathtub. And learn from it that a secondary vessel is not hot and does not cook. And learn from it with regard to oil that warming it is tantamount to cooking it.

...

On Shabbos, it is permissible to place onto a pot of hot water, a dish of food that is already fully cooked such as Panades or the like, in order to warm it, since he is not cooking in a usual manner. However it is definitely forbidden to place (food) under cloths that cover a water kettle. RAMA: similarly it is forbidden to place (food) on a Kirah even if it is Gerufa and Ketuma, as the sages only permitted Chazora (but not placing a pot for the first time), as has been explained above. Some (authorities) permit placing (a pot of food) into a Tanur used for baking on Erev Shabbos, when no food was left warming in it (it was merely used for baking on Erev Shabbos), only a small amount of heat remains and there need be no concern that this will cause it (the pot) to be cooked – provided (the food) has not cooled completely. Some, however, are stringent here, and (hold that) if the heat of the Tanur is so intense that it is of Yad soledes bo, it is forbidden. See below Siman 318. One may not tell a non-Jew to do anything that is forbidden to do himself. It is therefore forbidden to tell a non-Jew to heat up the pot (of food) that has cooled. If one does so, it is forbidden to eat it even cold. [Beis Yosef and the Teshuvos HaRashba] However, if the food has not cooled below the temperature at which it is edible, it may be eaten if the non-Jew heats it up. For this reason it is common practice to have non-Jews remove pots of food from ovens in which they have been stored to retain their heat, and place them next to or on top of a heating stove, and then have the (non-Jewish) maidservant light the stove, whereupon the food will become boiling hot once again. However it is forbidden to do this through a Jew. (Terumas HaDeshen) If, however, the pots are still hot they may be placed next to the heating stove. The reason is that, as has been explained, our ovens have a status of a Kirah, and placing it next to a Kirah, which is not Garuf Ve’katum, has the same law as placing directly on top of it when it is Garuf Ve’katum (which is permitted). It has already been stated that the customary practice is to be lenient (and permit) to do Chazora [returning a pot to the stove] even if the pot has been placed on the ground. Similarly, placing (a pot) next to an oven, which is not Garuf Ve’katum (is permitted) if the food is still hot and fully cooked. It is a widespread, accepted practice to permit this. See below Siman 318.

...

...

The Gemara now relates that there was once a certain baby whose warm water, which had been prepared for his Shabbat circumcision, spilled. Rabba said to them: Let them bring warm water for him from my house. Abaye said to him: But we did not establish an eiruv in the courtyard, so it is prohibited to carry the water.

Rabba said to him: Let us rely on the merging of alleyways, which may serve in place of a joining of courtyards in pressing circumstances such as these. Abaye said to him: But we did not establish a merging of alleyways either. Rabba replied: If so, let them instruct a gentile to bring the warm water for him, even though it is generally prohibited to instruct a gentile to perform labor for a Jew that involves a desecration of Shabbat.

What is implied? On the Sabbath, a Jew may instruct a gentile to climb a tree or to swim across water to bring him a shofar or a knife for circumcision. Similarly, [one may instruct a gentile] to bring hot water from one courtyard to another to wash a child or a person experiencing difficulty, although an eruv was not made to join them. The same applies in all similar situations.

1. One who cooks food on Shabbos [or performs any one of the other forbidden acts on Shabbos][Tur]; if done intentionally, the food is forbidden to eat forever, but other people are permitted to eat the food immediately after Shabbos. If done accidentally the food is forbidden to him during the day but may be eaten by everyone, including him, immediately after Shabbos. [If one ordered a non-Jew to perform a Melacha for oneself on Shabbos, see above Siman 307 se’if 20].