The halacha is that generally a keli shelishi does not cause bishul.

The Chazon Ish says that a keli shelishi (or revii) above yad soledes bo does cook those things that are kalei habishul.

A shiur by Rav Yosef Zvi Rimon explains the lenient view

Rashi (Shabbos 39a, s.v. De-sharei) explains that since we are not accustomed to cook in the sun there is no prohibition of bishul in the sun.

For our issue, it may be that the focus of the distinction between keli [sheini] and keli shelishi is the common custom. Most foods we cook in a keli rishon; some foods, such as tea, coffee, baby formula, etc., are commonly cooked in a keli [sheini]; while in a keli shelishi, one is not accustomed to cook at all. Naturally, we may say that even if on a practical level the foods that would cook in a keli [sheini] would also cook in a keli shelishi, there is no prohibition to cook them in a keli shelishi, because this is not derekh bishul, and it does not fall within the boundaries of the melakha.

So here we see that to transgress the issur of bishul on Shabbos, it is critical that the process is derekh bishul even though the food may be cooked in the keli shelishi. (I mean that the constitution of the food may be changed by being immersed in a keli shelishi which can easily be well over yad soledes bo.) Or to put it in other words, bishul is not cooking.

Someone observed cooking going on in a keli shelishi and wants to be extra strict and will not add anything to a keli shelishi which is above yad soledes bo.

How should we view such conduct? Is he inventing his own religion and should be convinced to abandon this view or is there room to look more kindly at his conduct?

  • 1
    If the person is being strict like the chazon ish then what's the problem?
    – Double AA
    May 31, 2020 at 16:06
  • The Chazon Ish restricts the chumra to the kalei habishul; this person will not add anything to a keli above yad soledes bo. May 31, 2020 at 16:14
  • 1
    How do you know what's not kalei habishul?
    – Double AA
    May 31, 2020 at 16:22
  • @DoubleAA maybe he's asking about those things we know aren't kalei habishul, can a person be machmir on that as well.
    – robev
    May 31, 2020 at 16:35
  • Thanks @robev . I have another thought too. The person in the question doesn't accept the idea of derekh bishul. So is his chumra legitimate? May 31, 2020 at 16:38

1 Answer 1


R. Eliezer of Metz in Yereim 274 writes explicitly that one should not put any food in a keli sheni nor in a keli shelishi (if they are at the temperature of yad soledet bo) as we do not know which types of food would cook in such a vessel:

יזהר אדם שלא להכניס בשבת שום דבר בכלי שני ואף בכלי שלישי שהיד סולדת בו שאין אנו בקיאים בדברים רבים וקשים מי הוא מתבשל בכלי שני ומי הוא שאינו מתבשל

It would seem that taking this opinion into account is a classic case of a chumra attempting to satisfy minority opinions.

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