Rabbi Roodyn

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The Mishna[1] says that cooking or baking is one of the 39 primary acts (melachos) that are forbidden on Shabbat. Cooking is defined as affecting a change in an object through the application of heat. As such, it is not limited to food and drink, as non food items (such as metals, when heated to red hot or wax, when melted) are also subject to the prohibition of cooking[2].

Before we start to discuss the laws of Bishul in detail, it is essential to clarify and define a number of concepts.

Cooking only takes place when food is heated to over 43°c, this is known as יד סולדת בו[3]. However there are cases where it will be forbidden to heat food to a lower temperature as will be discussed.

It is essential to know how the food was heated up. Halacha distinguishes between various methods of cooking, roasting, frying, boiling etc.

Halacha also makes the following distinctions, which are vital to understanding the halachos of bishul[4].

• Kli Rishon: כלי ראשון This is the vessel where the food or liquid is heated.
  • If it is still on the source of heat then certain strictures will apply, and it is known as a kli rishon she al gabei ha’aish.
  • If it is no longer on the fire it is known as a kli rishon she lo al gabei ha’aish.
• Iruy Kli Rishon עירוי כלי ראשון. Whilst an object is being poured from a kli rishon onto something else.
• Kli Sheni כלי שני. When an item is poured from a kli rishon, it comes to rest in a kli sheni.
• Iruy Kli Sheni עירוי כלי שני. Whilst an object is being poured from a kli sheni onto something else.
• Kli Shlishi כלי שלישי. When an item is poured from a kli rishon, it comes to rest in a kli shlishi.

It is also vital to distinguish between various types of food and liquid.

• A liquid that has not been fully cooked.
• A liquid that had been fully cooked but has cooled down to the point of only being slightly warm.
• A liquid that had been fully cooked but has now totally cooled down.
• A solid item that has not been fully cooked.
• A solid item that has been fully cooked, whether or not it is still hot.

The term ‘fire’ with regard to the laws of bishul includes ANY heat source[5], regardless of whether flame or heating elements are covered or exposed. As far as the laws of bishul are concerned, one can transgress the prohibition of cooking on any heat source, whether it is an oven, gas range, electric hob, hotplate, shabbos kettle, radiator.

Cooking is always forbidden on shabbos, and must never be confused with reheating which can be permitted in certain circumstances. The distinction between a covered and uncovered flame will be relevant to the laws of shehiya, chazara and hatmana, (these are Rabbinical decrees related to cooking, and will be discussed at length later).

• The prohibition of cooking applies to any liquid that is heated to יד סולדת בו, this is assumed to be 43°c[6].
• The prohibition of cooking applies to any solid heated to מאכל בן דרוסאי[7]. If a solid is heated to being 1/3 cooked, this is calculated by dividing the total cooking time for that object by 3[8]. Even though a solid has already reached this point (whether before or on Shabbat) nonetheless one may not heat it again so that it becomes more cooked[9]. It may however be left on the fire from before Shabbat to continue cooking (this is known as shehiya, and will be discussed at length later).

[1]  שבת עג.

[2]  רמב”ם הל’ שבת ט’:ו’.

[3]  דעת האג”מ. ועי’ בשש”כ א’:א’ בהערה ג’ שהביא דעות שמחמירות ששיעור יס”ב הוא פחות מהנ”ל. אבל השש”כ הכירע  למעשה כדעת הגרשז”א שבפחות ה45 מע’ לא נחשב יס”ב.

[4]  שש”כ א’:ג’.

[5]  שש”כ א’:ד’.

[6]  עי’ הערה 68.

[7]  אמנם שיש מחלוקת ראשונים אם מב”ד הוי חצי בישול או שליש בישול כמובא באו”ח רנ”ג ס”ק ל”ח מ”מ לענין איסור בישול לכתחילה מחמירים כדעה האומרת שליש בישול. משא”כ לגבי שהייה שלכתחילה מחמירים דהוי חצי בישול.

[8]  כדעת החזו”א.

[9]  או”ח שי”ח:ד’ ועי’ בה”ל ד”ה אפילו, שהאריך בזה שזה באמת מחולקת גדולה בין רבותינו הראשונים, ולכן למעשה אין לזוז מפסר השו”ע שהוא כדעת הרמב”ם ועוד חבל של ראשונים. אבל בדיעבד אין לאסור את התבשיל כיון שיש הרבה דעות בין הראשונים להתיר בכה”ג.