The Gemarah in Shabbos (97b) learns from the passuk in this week's parsha, (35:1) אלה הדברים , that there are thirty nine milachos that one must refrain from doing on shabbos. Rashi on the Gemarah explains that the gimatriyah of the word אלה is thirty six, plus the word 'devarim' is plural, and therefore implies two, and the ה of HAdivarim includes one more, that is three, and the , totaling thirty nine.
There is another Gemarah in Shabbos (49b) which brings an alternate source for the thirty nine milachos,
from the fact that the torah juxtaposed the parsha of shabbos to that of the building of the mishkan. We are to infer from this that those constructive acts used in the building of the mishkan are the milachos that are prohibited on shabbos.
If one transgresses one of the thirty nine milachos, the product of that milacha is forbidden to use. This is known as maiseh shabbos. There is a machlokes amongst the Tanaim whether this is forbidden by the Torah or mid'Rabanan. We paskin that it is forbidden mid'Rabanan. For example cooking is one of the thirty nine milachos, if one cooks on shabbos the food is forbidden to eat.
It is unclear as to the nature of the prohibition of the product of maiseh shabbos. Reb Chaim Soloveitchik (stencils 378) says that the prohibition of maiseh shabbos is different than other prohibitions, such as bassar b'chalav (cooked meat and milk).
With regard to the prohibition of bassar b'chalav, the Torah said that this item is forbidden (issur cheftzah). Meaning to say that by Torah law the item has a deficiency being that it is bassar b'chalav. However the prohibition of maiseh shabbos is a restriction on the person (issur gavrah) so as not to benefit from the milocha. The actual item is not intrinsically prohibited.
Another example of this type of prohibition is the prohibition not to eat on Yom Kippor where the actual food is not prohibited, rather the person is restricted from eating it.
Reb Moshe Feinstein (Igros Moshe O.C.1 126:3) argues and says that the product of maiseh shabbos is intrinsically forbidden, and similar to that of bassar b'chalav.
One difference that exists between these two opinions is, whether the pot that you cooked in will become forbidden as a result of the prohibited food giving off flavor into it. The flavor of that food remains in the walls of the pot, and is then expelled into the new food during its next use. This can render the new food forbidden as well. However this will only apply to a food item that is forbidden, for if the food is intrinsically permitted and only the person is restricted from it, it will therefore be permitted.
Therefore according to Reb Chaim, who holds that maiseh shabbos is an issur gavrah, the pot it was cooked in will be permitted. Whereas according to Reb Moshe the pot will be forbidden. In this situation R' Chaim Brisker ends up being the more lenient opinion.
Another difference between if the prohibition is an issur gavrah or issur cheftzah is, whether or not we can apply the rule of mitzvos lav lihanos nitnu to ma'asei shabbos (mitzvos were not given for the purpose of personal pleasure). A classic example of this rule is a lulav of issurai han'ah (forbidden to benefit from) that one may use for a mitzvah. The Rashba and other rishonim hold that even physical benefit derived during the performance of a mitzvah is permitted. Therefore if one were to perform a mitzvah with an item that was forbidden he would still be permitted to derive a physical pleasure from it. This only applies to an item that is intrinsically prohibited. However if the restriction is only on the person, the mitzvah cannot allow him to use the item.
Therefore, if one heated up a mikvah on shabbos, which is one of the thirty nine milochos, according to Reb Moshe that maiseh shabbos is intrinsically prohibited we may apply the rule of mitzvos lav lihanos nitnu and as a result one may enter into the mikvah for mitzvah purposes, even though a physical pleasure will be endured. Whereas according to Reb Chaim one may not enter into such a mikvah.
[The Magen Avraham (318:1) quotes a Rashba saying that the pot that one cooked in is in fact prohibited. This supports the opinion of Reb Moshe Feinstein.]
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Posted By Dovi milstein to KollelH blog at 2/25/2011 02:00:00 AM