If you've been to a Shabbat meal in an observant home, you may have noticed some distinctive things in the kitchen. The stove is covered with a thin metal plate (or electric hotplate), on which food is heating. There may be a slow cooker on the counter, and often a hot water urn as well.

These practices point to a central paradox about Shabbat: You can't cook food, and you can't heat it up as usual – but at the same time, one of the key aspects of Shabbat is enjoying a hot meal. In this and subsequent lessons, we will learn how to navigate this issue. To do so, we will need to understand what many consider the 'mother of all melachot', Bishul1 (cooking). It will require six lessons to cover all the material, but we will take it one step at a time. And with God's help, we will succeed in getting a good grasp of the concepts and applications.

What is "Cooking" in Halacha?

Cooking (or baking, as this melacha is also called2) is the final act in the 'Order of Bread', the series of labors we've been learning up to this point. Halachically, Bishul is defined as using heat to affect a positive change in the physical structure of an object. The classic case is baking bread, which is the paradigm we've been following in this course. As we'll see, though, the melacha of Bishul applies to foods as well as non-foods.3

Let's begin by understanding the components of this melacha.

(1) The type of heat used

When we talk about heat, we mean fire or red-hot metal.4 'Fire' includes not only a classic open flame, but also fires derived from gas and electricity.5

(2) When Bishul takes place

Cooking is a process, not an instant occurrence. Therefore, the halacha states that you have only done an act of Bishul when the cooking is completed. When is this? That depends on whether the item is a solid or a liquid.

With solid foods, Bishul is accomplished as soon as the item is somewhat edible.6 The Talmud describes this as 'the food of Ben Drusai', named after a well-known highwayman who had to eat his food partially cooked since he was always on the run.7 Once a solid food has reached this point, it is deemed cooked.

With solid non-foods, "cooking" means either causing a soft item to harden (for example, heating pottery in a kiln), or causing a hard item to soften (for example, melting metal). Once this change begins to occur, the act of Bishul has been done.8

When it comes to liquids, no apparent change takes place when the liquid is heated. Here, then, we look only to the level of heat itself: Bishul takes place when it is heated to the point of 'yad soledet bo' – that is, the point where you'd instinctively draw back your hand if you touched it.9 The most commonly-accepted definition of this is 113°F or 45°C.10

(3) What other actions constitute Bishul

So far, we've been imagining a scenario where you take raw food and apply heat so that it will cook. There are other ways to do an act of Bishul, which happen once the food is already in the process of being cooked.

In general, once something is cooking, any action that will cause the cooking to take place more rapidly is itself an act of Bishul.11

Some examples:12

  • Stirring a pot of food that is cooking – this allows for the heat to be better distributed
  • Putting a lid on a pot that is on the fire – this concentrates the heat within the pot13
  • Closing an oven door – this better insulates the heat within that space

All of these actions are therefore not permitted on Shabbat.

Indirect Heat

Here's where the melacha of Bishul gets really interesting. To this point, we've been discussing situations where the item being cooked is connected to a heat source (e.g., on a stove-top). However, once the item is removed from that heat source, the story is not over: Halachically, "cooking" can still occur. This is because cooking utensils retain heat even after they are removed from the fire, and this residual heat itself has the power to cause Bishul.

We now need to understand some basic terms related to utensils. To help us, let's invite back our friend Melissa, whom we visited when discussing Dosh.

It's Friday night, and Melissa's kitchen smells very good. On her stove,14 she has a pot of soup and some Pyrex dishes containing meat and other good things. Each of the utensils on the stove is considered a first vessel (Hebrew, kli rishon). Many of the activities covered under Bishul take place in a first vessel.

Actually, there are two levels:

  • First vessel on the fire (kli rishon al ha'aish) – i.e. it is directly connected to a source of heat
  • First vessel not on the fire (kli rishon shelo al ha'aish) – even after being removed from the source of heat, the vessel still retains its status as a first vessel, albeit with a few practical differences that we will later explore

When serving the soup, Melissa ladles a portion into each person's bowl.15 Each bowl then becomes a second vessel (kli sheni), because it has received the hot food from the pot on the fire. Since the bowl was never physically in contact with a heat source, we view this second vessel as less capable of causing Bishul, as compared to a first vessel, for two reasons:

  1. the food in the second vessel no longer has the hot [metal] walls of the first vessel to sustain its level of heat, and
  2. the cold walls of the second vessel actually cool the food that has been poured into it16

Let's say Melissa wants to use her beautiful new soup tureen. If she poured the hot soup from the pot (a first vessel) into the tureen (a second vessel) and then served it to everyone, the bowl each person uses would be... that's right, a third vessel (kli shelishi). Every time we remove a cooked item further from the heat that cooked it, we move down another 'level' – because the further away the vessel is from the fire, the less capable it is of cooking something else it touches.

(Theoretically, this chain can go on endlessly. In practice, we don't usually get past a third vessel, since there are few if any halachic ramifications.)

To review: one is considered to have done an act of Bishul when the cooking is completed:

  • With solid foods – Bishul is accomplished as soon as the item is somewhat edible (like the food of Ben Drusai – 1/3 or 1/2 cooked).
  • With solid non-foods – Bishul means causing a soft item to harden or causing a hard item to soften. The Melacha is done once this change begins to occur.
  • With liquids – Bishul takes place when it is heated to Yad Soledet Bo, the point where you'd instinctively draw back your hand if you touched it.

With this background, in our next lesson we will explore the halachot that apply to each category of vessels.

  1. Pronounced bee-SHOOL.
  2. In Hebrew, ‘ofeh’.
  3. Talmud – Shabbat 106a; Rambam (Shabbat 9:6); 39 Melochos, p. 553.
  4. Orach Chaim 318:3.
  5. Rambam (Shabbat 9:6); Halachos of Shabbos, XIV:A.5 (p. 245). The topic of solar heat will be discussed in Lesson #24.
  6. Talmud – Shabbat 20a. This is considered a sufficient change to satisfy the core definition of Bishul we mentioned earlier.
  7. There is a difference of opinion whether this means half-cooked (Rambam – Shabbat 9:5), or one-third cooked (Rashi – Shabbat 20a).
  8. Rambam (Shabbat 9:6); 39 Melochos, p. 556; Halachos of Shabbos, XIV:B.1-3 (p. 270-72).
  9. Talmud – Shabbat 40a with Rashi (s.v. “Soledet”); 39 Melochos, p. 557. Note that further heating of the liquid may still be an act of Bishul. See ibid, p. 558.
  10. Shemirat Shabbat K’Hilchato 1:1. Other opinions range from 104-120ºF. 39 Melochos, p. 557; Halachos of Shabbos, XIV:A.4 (p. 243).
  11. Talmud – Beitza 34a; Orach Chaim 254:4; 39 Melochos, p. 559.
  12. On all of these cases, see Halachos of Shabbos, XIV:B.6-8. These apply when the food involved is not yet fully cooked.
  13. Shu”t Igros Moshe (Orach Chaim 4:10:6).
  14. Which is covered by a thin metal place known as a blech – something we’ll get to later.
  15. The ladle itself is a type of vessel, which we’ll discuss further on.
  16. Tosfot (Shabbat 40b, s.v. “U’Shema”)