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    Chapter 2 · The 39 Avot Melakhot

    Cooking and baking - stages of liability

    Lesson 17 of 28 26 min

    Cooking is a toladah of baking. The liability measure: "ke'ma'achal ben Drusai" - a third or half cooked. Hot plate and pot laws build on this and on "no cooking after cooking" in dry vs. liquid foods.

    Lesson goals
    • 01Define "ma'achal ben Drusai" (Shabbat 20a)
    • 02Distinguish dry vs. liquid in "no cooking after cooking"
    • 03Know hot plate and bal'anya bounds
    01

    The Melachah of Bishul: Av and Toladah

    We are building our understanding of the melachah of Bishul (cooking), one of the 39 Avot Melachot. Cooking is a Torah prohibition on Shabbat, and it is fundamental to daily life. Let's begin by decoding the relationship between cooking and baking.

    תלמוד בבלי שבת עג ע"א
    האופה והמבשל והמטגן והמשרב והמצלה והמבושל והמטוגן והמצלי... כל אלו אב מלאכה אחת הן.

    One who bakes, or cooks, or fries, or boils, or roasts... all these are one primary melachah.

    Insight

    The Gemara clarifies for us that all forms of softening and changing food through heat – whether by direct fire, boiling water, or oil – are all considered one melachah, the melachah of cooking (or baking, which is the 'Av'). This is a key principle for understanding all prohibitions related to heat.

    02

    Measure of Liability: 'Ke'ma'achal Ben Drusai'

    When does a person become liable for cooking on Shabbat? Not every slight warming is considered complete cooking. The Torah established a specific criterion.

    תלמוד בבלי שבת כ ע"א
    בישל כל צרכו – חייב; לא בישל כל צרכו – פטור. מאי כל צרכו? אמר רב יוסף: כדי שיאכלנו בן דרוסאי.

    If he cooked it to the extent it is fully cooked – he is liable; if he did not cook it to the extent it is fully cooked – he is exempt. What is 'to the extent it is fully cooked'? Rav Yosef said: To the extent that Ben Drusai would eat it.

    כמאכל בן דרוסאיKe'ma'achal Ben Drusai
    The minimum measure of cooking at which food is considered 'cooked' for Shabbat liability. This is approximately one-third to half cooked, depending on the food and custom.
    Insight

    The determination of 'Ma'achal Ben Drusai' teaches us an important principle: not every change by heat incurs liability. Only a significant change, one that makes the food edible (even if not perfectly cooked), triggers the Torah prohibition. Before that point, it is a Rabbinic prohibition of 'cooking to its full extent'.

    03

    No Cooking After Cooking: Dry vs. Liquid

    Another foundational principle in the laws of cooking is 'Ein Bishul Achar Bishul' (no cooking after cooking). This principle states that one cannot cook food that has already been fully cooked. But does it apply equally to all types of food?

    תלמוד בבלי שבת מ ע"ב
    אמר רבא: כל דבר שנתבשל כל צרכו – אין בו משום בישול אחר בישול. מאי כל צרכו? כדי שיאכלנו בן דרוסאי. והוא הדין לכל דבר שנתבשל כל צרכו.

    Rava said: Any item that has been cooked to its full extent – there is no cooking after cooking for it. What is 'to its full extent'? To the extent that Ben Drusai would eat it. And the same applies to anything that has been cooked to its full extent.

    Insight

    The Gemara clarifies that the principle of 'Ein Bishul Achar Bishul' applies to dry foods. Once they are cooked (even to the 'Ma'achal Ben Drusai' stage) – they cannot be cooked again. However, regarding liquid foods, some halachic authorities hold that 'there is cooking after cooking' as long as they have not reached a renewed boiling point, or if they have completely cooled down.

    04

    Practical Applications: Hot Plate and Bal'anya

    Understanding the principles of 'Ma'achal Ben Drusai' and 'Ein Bishul Achar Bishul' is crucial for applying Shabbat laws in the modern kitchen, especially with appliances like Shabbat hot plates and bal'anyas (water urns).

    1. 1Dry food fully cooked before Shabbat: It is permissible to place it on a hot plate on Shabbat to keep it warm or warm it slightly, because there is no cooking after cooking for it.
    2. 2Liquid food fully cooked before Shabbat: If it is hot (yad soledet bo – about 45 degrees Celsius), it is permissible to place it on a hot plate. If it has completely cooled, some are stringent to prohibit reheating due to 'cooking after cooking' in liquids.
    3. 3Food not fully cooked before Shabbat: It is absolutely forbidden to place it on a hot plate, as it will continue to cook and pass the 'Ma'achal Ben Drusai' threshold on Shabbat, which is a Torah prohibition.
    Insight

    The distinction between dry and liquid is critical. While a dry food fully cooked before Shabbat cannot be cooked again, a liquid food might undergo 'cooking after cooking' if it has completely cooled, and reheating it would be prohibited. Therefore, a rule of thumb is to try to leave liquid foods warm on the hot plate from Erev Shabbat.

    Practice

    May you place a frozen challah on the hot plate Shabbat morning? Justify.

    Lesson wrap-up

    The Shabbat kitchen asks the cook to be a small posek. Know the rules - cook with joy.

    Check your understanding

    Test yourself before marking the lesson complete.

    Question 1 of 4

    What is the measure of 'Ma'achal Ben Drusai' concerning cooking on Shabbat?

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