Arukh HaShulchan Yomi · Expert – Beit Midrash Analysis · Standard
Arukh HaShulchan, Orach Chaim 318:26-31
Sugya Map
The sugya of Bishul Achar Bishul (cooking after cooking) on Shabbat, as articulated in Arukh HaShulchan, Orach Chaim 318:26-31, delineates the boundaries between physical transformation and thermal reactivation. The primary issues, their corresponding nafka minot (practical differences), and the foundational sources are structured as follows:
- The Status of Partially Cooked Dry Foods (Davar Yavesh): Does an item cooked to the level of Ma'achal Ben Derusai (one-third or one-half cooked) still present a biblical prohibition of Bishul for the remaining fraction?
- Nafka Mina: Reheating a half-baked loaf of bread or a partially roasted piece of meat on a heat source on Shabbat.
- Primary Sources: Shabbat 34a, Shabbat 145b, Mishneh Torah, Sabbath 9:3.
- The Reversibility of Liquid Cooking (Davar Lach): Does the cooling of a fully cooked liquid (Lach Shenitztanen) retroactively undo its cooked status, thereby rendering subsequent reheating a biblical violation of Yesh bishul achar bishul belach?
- Nafka Mina: Placing cold soup or water onto a hot plate or blech on Shabbat.
- Primary Sources: Shabbat 40b, Ran on Shabbat 40b, Shulchan Arukh, Orach Chaim 318:4.
- The Halakhic Mechanics of a Solid Mass (Davar Gush): Does a solid, hot food item (e.g., a potato or piece of meat) retain the status of a Keli Rishon (primary vessel) even when transferred to a Keli Sheni (secondary vessel) or Keli Shelishi (tertiary vessel)?
- Nafka Mina: Pouring cold spices, oil, or ketchup onto a hot potato sitting on a serving plate.
- Primary Sources: Shabbat 42b, Shulchan Arukh, Yoreh Deah 105:2, Magen Avraham 318:45.
- Inter-Melahah Transitions (Bishul Achar Afiyah): Is there a prohibition of cooking an item that has already been baked (Afiyah), or vice versa?
- Nafka Mina: Dipping dry, baked bread or matzah into a boiling pot of soup (Keli Rishon).
- Primary Sources: Menachot 55b, Shulchan Arukh, Orach Chaim 318:5.
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Text Snapshot
The following key passages from the Arukh HaShulchan illustrate the linguistic nuances and conceptual pivots of his analysis:
Arukh HaShulchan, Orach Chaim 318:26
"...ודבר יבש שנתבשל כל צרכו – אין בו משום בישול אחר בישול, ואפילו נצטנן לגמרי... אבל אם לא נתבשל כל צרכו, אף על פי שנתבשל כמאכל בן דרוסאי – יש בו משום בישול לגמור את בישולו..." "And a dry item that was fully cooked—there is no issue of cooking after cooking, even if it has cooled down completely... But if it was not fully cooked, even though it was cooked to the level of Ma'achal Ben Derusai, there is an issue of cooking to complete its cooking..."
Arukh HaShulchan, Orach Chaim 318:27
"ודבר לח שנצטנן – יש בו משום בישול אחר בישול... וכל זמן שלא נצטנן לגמרי, אף על פי שאין היד סולדת בו – אין בו משום בישול לדעת הרמ"א..." "And a liquid item that has cooled down—there is an issue of cooking after cooking... and as long as it has not cooled down completely, even though the hand does not shrink from it (yad soledet bo), there is no issue of cooking according to the Rama..."
Linguistic Nuance
The Arukh HaShulchan uses the phrase "לגמור את בישולו" (to complete its cooking) to define the continuing Melahah of Bishul for partially cooked items. In his analysis of Davar Lach, his emphasis on "שלא נצטנן לגמרי" (not completely cooled) as the threshold for the Rama’s leniency hinges on a thermodynamic reality rather than a formalistic binary of Yad Soledet Bo. He shifts the focus from the subjective sensation of heat to the objective presence of residual thermal energy.
Readings
The conceptual matrix of Bishul Achar Bishul divides the Rishonim and Acharonim into competing camps regarding the physical and metaphysical definition of "cooking."
[Thermal Processing of Food]
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[Dry (Yavesh)] [Liquid (Lach)]
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[Irreversible Change] [Reversible Change]
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No Re-cooking (Even Does Cooling Undo Cooking?
if cold) |
-------------------------
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[Yes (Rambam)] [No (Ran/Rashba)]
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Re-heating is Only if cooled
Biblical completely
Reading 1: The Metaphysics of Liquid vs. Solid Cooking (Mechaber vs. Rama)
The dispute between Rabbi Yosef Karo Shulchan Arukh, Orach Chaim 318:4 and the Rama Shulchan Arukh, Orach Chaim 318:15 regarding Lach Shenitztanen (cooled liquid) represents an ontological debate on the nature of liquids.
The Rambam Mishneh Torah, Sabbath 9:3, followed by the Mechaber, rules that if a cooked liquid has cooled down, the prohibition of Bishul returns in full force. The Ran Ran on Shabbat 40b and the Rashba, representing the lenient view, hold that once an item has been cooked, the historical act of cooking cannot be undone; thus, Ein bishul achar bishul applies to liquids as well as solids.
The Arukh HaShulchan Arukh HaShulchan, Orach Chaim 318:27 conceptualizes this split by analyzing the physical difference between Lach and Yavesh.
A dry food (Yavesh) undergoes an irreversible chemical and structural transformation when cooked (e.g., denaturing of proteins or gelatinization of starches). Once this structural transformation occurs, subsequent heating does not alter the food's essential state; it merely increases its temperature.
A liquid (Lach), however, undergoes primarily a thermodynamic change rather than a structural one. The culinary utility of a liquid is intrinsically bound to its active state of heat. A cold soup is functionally raw in terms of its consumption paradigm.
Therefore, the Rambam and Mechaber hold that when a liquid cools, its "cooked" status (shem bishul) evaporates. Reheating it is not merely adding heat; it is reconstituting its identity as a cooked food.
The Rama, however, adopts a more historical-physical view: once the liquid has been boiled, the water molecules have been processed, and the subsequent drop in temperature is a temporary, external state that does not retroactively erase the historical reality of the initial boiling.
The Arukh HaShulchan Arukh HaShulchan, Orach Chaim 318:28 introduces a crucial nuance to the Rama's view. Even the Rama agrees that if a liquid cools down completely (niztanen legamri), reheating it is biblically forbidden. The lenient position of the Ran only applies if there is still some residual warmth (poking pach) in the liquid.
Why should residual warmth below the threshold of Yad Soledet Bo (typically defined as approximately 45°C/113°F) prevent the prohibition of Bishul?
According to the Arukh HaShulchan, as long as the liquid retains some warmth, it has not fully reverted to its raw state. The chain of the initial cooking has not been broken. The heat present, though insufficient to cook other items, maintains the food's identity as "warm food" rather than "cold liquid."
Reading 2: The Ontology of Davar Gush (Maharshal vs. Arukh HaShulchan)
A major debate exists regarding the status of a Davar Gush (a dense, solid piece of hot food, such as a potato or meat). The Gemara Shabbat 42b discusses the cooling power of vessels (Keli Rishon, Keli Sheni), but does not explicitly address whether a solid mass behaves differently than a liquid.
The Maharshal, cited in the Magen Avraham Magen Avraham 318:45, argues that a Davar Gush retains its status as a Keli Rishon even when placed into a Keli Sheni or Keli Shelishi. Because of its solid density, it does not circulate its heat or lose energy to the walls of the vessel in the way a liquid does. It acts as an independent thermal battery, capable of cooking (meflit u-mevashel) anything placed in direct contact with it.
The Arukh HaShulchan Arukh HaShulchan, Orach Chaim 318:29 offers a highly original and thermodynamically precise reading of the Davar Gush dynamic. He questions the ontological classification of the Gush: Is it a Keli Rishon because of its identity (formal halakhic categorization), or is it merely a Keli Rishon because of its functional thermal capacity?
He argues that a Davar Gush cannot be classified as a true Keli Rishon in a formal sense, because a Keli Rishon by definition is a vessel that sat directly on the fire. Rather, the Gush is treated strictly because we suspect it possesses the physical power to cook.
From this distinction, the Arukh HaShulchan derives a major leniency: if the Davar Gush is placed into a liquid, or if liquid is poured over it, the thermal retention of the solid is immediately disrupted. The liquid surrounding the Gush acts as a heat sink, rapidly conducting heat away from the surface of the solid and dispersing it.
Therefore, once the Gush is immersed in a liquid within a Keli Sheni, it loses its status as a Keli Rishon and can no longer cook. This stands in contrast to the Maharshal, who would treat the Gush as a Keli Rishon under all circumstances until it cools below Yad Soledet Bo.
Reading 3: The Boundaries of Thermal Processing (Bishul Achar Afiyah)
The sugya of Bishul Achar Afiyah (cooking after baking) or Afiyah Achar Bishul (baking after cooking) addresses whether different modalities of dry-heat processing (baking, roasting) and wet-heat processing (cooking) are halakhically interchangeable.
The Yereim, cited by the Hagahot Maimoniyot Mishneh Torah, Sabbath 9:3, holds that there is a biblical prohibition of Bishul Achar Afiyah. If one takes baked bread and cooks it in a liquid within a Keli Rishon, they have violated the Melahah of Bishul.
The rationale is that baking and cooking are distinct physical processes that produce different culinary results: baking dries and crisps, while cooking softens and saturates. Therefore, changing the state of a food from baked to cooked constitutes a new Tikkun (improvement) of the food, which constitutes Bishul.
The Rosh and the Rambam, however, hold that Ein bishul achar afiyah. Both are sub-categories of the overarching concept of processing food via fire (tikkun ma'achal al yedei ha-esh). Once a food is fully edible through fire-processing, no subsequent fire-processing can trigger a biblical violation.
The Arukh HaShulchan Arukh HaShulchan, Orach Chaim 318:31 analyzes this debate and highlights the Rama's compromise position Shulchan Arukh, Orach Chaim 318:5: we rule stringently that there is Bishul Achar Afiyah in a Keli Rishon, but we are lenient in a Keli Sheni.
The Arukh HaShulchan asks: If the Yereim is correct that baking and cooking are fundamentally different Melahot, why should a Keli Sheni be permitted? We know that Keli Sheni does not cook, but we also suspect that certain easily cooked items (Kalei HaBishul) can cook even in a Keli Sheni Shabbat 145b. Bread, being porous and soft, should be classified as the ultimate Kalei HaBishul!
To resolve this, the Arukh HaShulchan proposes that the stringency of the Yereim is not a robust, absolute biblical prohibition when applied to fully edible baked foods. Rather, because the food is already fully edible, any subsequent cooking is only a marginal change in form (shinui tzurah).
Therefore, we do not apply the extreme stringency of Kalei HaBishul to bread in a Keli Sheni. The baseline rule that a Keli Sheni cannot cook (Ein Keli Sheni mevashel) remains intact to permit placing bread into a secondary vessel of soup, even if the soup is boiling hot.
Friction
The Thermodynamic Paradox: Convection, Conduction, and Tat'ah Gavar
The primary friction in the laws of Davar Gush emerges when we attempt to reconcile the thermodynamic behavior of solids with the classical halakhic principle of Tat'ah Gavar (the lower element overcomes the upper element) Shabbat 75b.
According to Tat'ah Gavar, when a hot item and a cold item come into contact, the one situated on the bottom dictates the immediate thermal transfer. If hot food is poured onto a cold plate, the cold plate (being on the bottom) cools the outer layer of the hot food, preventing it from cooking.
How, then, can the Maharshal and the Rama rule that a Davar Gush (such as a hot potato) placed on a cold plate (Keli Sheni) can cook spices placed on top of it? If the potato is sitting on a cold plate, the principle of Tat'ah Gavar should dictate that the cold plate cools the potato, neutralizing its ability to cook!
Terutz A (The Pri Megadim's Density Model)
The Pri Megadim Mishnah Berurah 318:45 resolves this by distinguishing between liquid-to-solid heat transfer and solid-to-solid heat transfer.
The principle of Tat'ah Gavar was formulated primarily for liquids. When hot liquid is poured onto a cold surface, the liquid's fluid nature allows for rapid convection, and the cold bottom vessel quickly cools the entire mass of the liquid.
A Davar Gush, however, is solid and dense. It does not experience convection. Heat transfer within a solid occurs solely via conduction, which is a slow process.
Therefore, while the cold plate cools the microscopic bottom layer of the potato that is in direct contact with it, the core of the potato remains at its original boiling temperature. When spices are placed on top of the potato, they are in contact with a surface that is still drawing heat from the hot core. Thus, Tat'ah Gavar is localized and fails to neutralize the thermal mass of the Gush.
Terutz B (The Arukh HaShulchan's "Kefiyah" / Pressure Model)
The Arukh HaShulchan Arukh HaShulchan, Orach Chaim 318:29 offers a different resolution, focusing on the mechanics of contact. He argues that a Davar Gush only cooks when there is kefiyah—physical pressure or tight packing that traps the heat between the solid food and the spices.
When spices are merely sprinkled on top of a hot potato, they do not cook because the air circulating around them cools them down. The potato only has the power of a Keli Rishon if the food placed on it is pressed tightly against it, preventing air from circulating.
This explains why we do not apply Tat'ah Gavar to neutralize the Gush: the heat transfer from the Gush to the spice is direct and immediate at the point of pressurized contact, bypassing the cooling effect of the distant cold plate at the bottom.
The Clash of Shabbat vs. Kashrut: Bishul vs. Beli'ah
A second major friction point is the systemic contradiction between the rules of Davar Gush in Hilkhot Shabbat and Hilkhot Issur V'Heter (Kashrut).
In Hilkhot Issur V'Heter Shulchan Arukh, Yoreh Deah 105:2, we rule that a Davar Gush of non-kosher meat has the power to transfer its taste (Beli'ah and Pliatah) to a kosher vessel or food item even in a Keli Sheni or Keli Shelishi.
However, the primary mechanism of Kashrut is taste transfer (Pliat Or), which requires a lower thermal threshold than the actual cooking of food (Bishul) required for a Shabbat violation.
How can we use the rules of Kashrut—where the threshold of taste transfer is low—to establish a strict rule for Shabbat, where a biblical violation requires actual cooking (Bishul)?
[Thermal Transfer Thresholds]
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[Kashrut (Yoreh Deah)] [Shabbat (Orach Chaim)]
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Requires: Taste Transfer Requires: Actual Cooking
(Pliat Or / Beli'ah) (Melahat Bishul)
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Lower Thermal Threshold Higher Thermal Threshold
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Davar Gush transfers taste Does Davar Gush actually
easily in Keli Sheni cook? (Rama: Yes /
Arukh HaShulchan:
Only via pressure)
Terutz
To resolve this, we must bifurcate the definition of Bishul.
There is Bishul as a Melahah (the creative act of baking/cooking), and there is Bishul as a physical state of heat retention.
The Rama Shulchan Arukh, Orach Chaim 318:15 imports the stringency of Davar Gush from Yoreh Deah to Shabbat because, in terms of physical heat retention, the Gush does not care whether its heat is transferring taste or cooking fibers; the thermal energy remains concentrated.
However, the Arukh HaShulchan Arukh HaShulchan, Orach Chaim 318:29 limits this import. He argues that while we are strict on Shabbat to treat a Gush like a Keli Rishon, this is only l'chatchilah (rabbinically, as a safeguard).
M'ikar hadin (fundamentally), a Davar Gush cannot generate a biblical violation of Bishul in a Keli Sheni because the definition of Melahat Bishul on Shabbat requires a standard cooking environment—namely, a vessel that has been heated by the fire (Keli Rishon). A solid piece of food, no matter how hot, is not a vessel.
By framing the Shabbat status of Davar Gush as a rabbinic stringency modeled after Kashrut, rather than an absolute biblical reality of Bishul, the Arukh HaShulchan elegantly resolves the systemic clash between Orach Chaim and Yoreh Deah.
Intertext
Talmudic Foundations: Shabbat 145b and Menachot 55b
The foundational text for Bishul Achar Bishul is the Mishnah in Shabbat 145b:
"כל שבא בחמין מלפני השבת – שורין אותו בחמין בשבת. וכל שלא בא בחמין מלפני השבת – מדיחין אותו בחמין בשבת, חוץ מן המליח הישן..." "Anything that came into hot water before Shabbat may be soaked in hot water on Shabbat. And anything that did not come into hot water before Shabbat may only be rinsed with hot water on Shabbat, except for old salted fish..."
This Mishnah establishes the principle that pre-cooked items (she-ba be-chamin) are no longer subject to the prohibition of Bishul. The Gemara there clarifies that "soaking" refers even to placing the item into a Keli Rishon that has been removed from the fire.
However, the Gemara does not distinguish between dry and liquid foods. The bifurcation of Lach and Yavesh was introduced by the Rishonim based on Shabbat 40b, where the Gemara discusses heating oil and water, noting that water presents a stricter cooking profile than oil, and that heating cold water to the point of Yad Soledet Bo constitutes a violation of Bishul.
To understand the friction of Bishul Achar Afiyah (cooking after baking), we must look to Menachot 55b, which discusses the preparation of the Minchat Ma'afeh Tanur (the baked meal-offering). The Gemara discusses whether a baked offering that is subsequent crumbled and cooked in a liquid violates the rules of meal-offerings.
The halakhic midrash derived from this discussion forms the basis of the Yereim's position: baking and cooking are structurally distinct, and one does not neutralize the other.
Modern Applications: Igrot Moshe and the Viscosity of Ketchup
In modern responsa, the status of highly viscous liquids—such as ketchup, chocolate syrup, or condensed soup—presents a major application of the Arukh HaShulchan's thermodynamic models.
Rav Moshe Feinstein Igrot Moshe, Orach Chaim 4:74 addresses whether one may pour ketchup onto a hot potato (Davar Gush) on Shabbat.
[The Ketchup Dilemma]
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[Is it a Liquid (Lach)?] [Is it a Solid (Yavesh)?]
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Reheating when cold is No cooking after cooking,
forbidden (Mechaber) even if cold (Rama/Mechaber)
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Flows, but highly viscous Thick, holds its shape
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[Halakhic Ruling]
Does viscosity = solid state?
- Igrot Moshe: It is a liquid;
cannot put on Davar Gush.
- Arukh HaShulchan: If it has
solid characteristics, maybe lenient.
If ketchup is classified as a Davar Lach (liquid), then because it has cooled down completely, pouring it onto a hot potato would violate Bishul according to the Mechaber, and even according to the Rama (since it is cold and the potato acts as a Keli Rishon).
If ketchup is classified as a Davar Yavesh (dry/solid), then since it was fully cooked during its pasteurization and manufacturing process, there is Ein bishul achar bishul, and pouring it onto the hot potato would be entirely permitted.
Rav Moshe Feinstein rules stringently, classifying ketchup as a liquid because of its flow characteristics (viscosity). Even though it is thick, it eventually flows and spreads, which defines it halakhically as a liquid.
However, using the Arukh HaShulchan’s model Arukh HaShulchan, Orach Chaim 318:27, one could argue for a lenient ruling. The Arukh HaShulchan posits that the entire reason Davar Lach is subject to Bishul Achar Bishul is that its culinary essence is its heat, and it cools down in a way that reverts it to a raw-like state.
Ketchup, however, is consumed cold as a condiment; its culinary utility does not depend on its thermal activation. Therefore, even if it has liquid properties, its "cooked" status is not lost upon cooling, because its cold state is a fully realized culinary form. Thus, it should be treated as a Davar Yavesh, allowing one to pour it onto a Davar Gush.
Psak/Practice
The contemporary application of these rulings divides Sephardic and Ashkenazic practices, heavily influenced by the conceptual moves of the Shulchan Arukh and the Arukh HaShulchan.
Sephardic Practice (Following the Shulchan Arukh)
- Lach Shenitztanen: There is an absolute prohibition of Yesh bishul achar bishul belach once a liquid has cooled below Yad Soledet Bo. Therefore, one may not place cold soup, gravy, or water onto a hot plate, even if it was previously boiled.
- Davar Gush: The Shulchan Arukh does not explicitly codify the stringency of Davar Gush in Hilkhot Shabbat. Therefore, Sephardic authorities (such as Rav Ovadia Yosef) rule that a hot potato or piece of meat in a Keli Sheni does not behave like a Keli Rishon. One may pour cold oil or spices directly onto it.
Ashkenazic Practice (Following the Rama and Arukh HaShulchan)
- Lach Shenitztanen: The Rama Shulchan Arukh, Orach Chaim 318:15 is lenient as long as the liquid has not cooled down completely. If the soup is still lukewarm, one may place it on a heat source (provided there is no issue of Chazarah—returning to a direct flame).
- Davar Gush: We are stringent to treat a Davar Gush as a Keli Rishon. One may not place raw spices on a hot potato in a Keli Sheni. However, following the Arukh HaShulchan's ruling Arukh HaShulchan, Orach Chaim 318:29, if the potato is immersed in liquid, or if one is pouring a liquid onto it, the stringency of Davar Gush is lifted.
Contemporary Summary Table
| Food Type / Scenario | Sephardic Halakha (Mechaber) | Ashkenazic Halakha (Rama / Arukh HaShulchan) | Halakhic Mechanism |
|---|---|---|---|
| Lukewarm Soup (Below Yad Soledet) | Forbidden to heat | Permitted to heat (if not fully cold) | Yesh/Ein bishul belach with residual heat |
| Fully Cold Soup | Forbidden to heat (Biblical) | Forbidden to heat (Biblical) | Reheating cold liquid is a new Bishul |
| Spices on Hot Potato (Keli Sheni) | Permitted | Forbidden | Davar Gush status in Shabbat laws |
| Bread in Hot Soup (Keli Sheni) | Permitted | Permitted | Ein Keli Sheni mevashel for Bishul Achar Afiyah |
Meta-Psak Heuristics of the Arukh HaShulchan
The Arukh HaShulchan’s methodology in these paragraphs reveals his classic meta-psak heuristic: the defense of common practice through thermodynamic and physical realism.
Rather than imposing abstract, formalistic stringencies that ignore the physical reality of the kitchen, Rabbi Yechiel Michel Epstein constantly analyzes how heat actually behaves.
His ruling that liquid surrounding a solid potato neutralizes its Davar Gush status is a prime example of this realism. He refuses to allow a rabbinic stringency (Davar Gush) to expand beyond its physical justification. If the physical reason for the stringency (heat retention) is neutralized by a surrounding liquid, the halakha must adapt accordingly.
Takeaway
The debate over reheating food on Shabbat hinges on a fundamental question: Is cooking defined by an irreversible change to the food's physical structure, or by the active presence of thermal energy?
For dry foods, the structural change is permanent, meaning they cannot be cooked again. For liquids, the state of the food is tied to its temperature, meaning that once they cool down, they are considered uncooked once more.
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