1) RETURNING A POT TO ITS PLACE OF "HATMANAH"
OPINIONS: The Mishnah states that if a pot was surrounded by insulating material in such a way that when one lifts the pot, the material around it falls to where the pot was resting, he may not return the pot to its place. The Gemara (50b) says that even the Rabanan agree that if the material on the sides falls in, one may not return the pot. Why is one prohibited from returning the pot in such a case?
(a) RASHI explains that one may not return the pot to its place of Hatmanah because the material (such as strips of wool) in which it was insulated is Muktzah, and one may not move the material in order to return the pot to its place.
(b) The RAMBAM (in Perush ha'Mishnayos) says that even if one uses non-Muktzah objects for Hatmanah, he still may not return the pot to its place. The reason is that since one needs to clear away the area that became covered by the insulating material, he is considered as though he is doing a new Hatmanah (and not merely continuing the previous Hatmanah). The BEIS YOSEF says that this is also the ruling of the Rambam in Hilchos Shabbos (although this ruling is not written explicitly there). The Rambam is more stringent than Rashi because according to Rashi one may move non-Muktzah material in order to return a pot to its place, while according to the Rambam one may not.
HALACHAH: The SHULCHAN ARUCH (OC 259:3) mentions both opinions. Although the VILNA GA'ON cites a proof for the Rambam's stringent opinion from the Yerushalmi, the BI'UR HALACHAH writes that the Shulchan Aruch seems to side with the first opinion, since it mentions the Rambam's opinion only as a "Yesh Omrim" -- "there are those who say."

49b----------------------------------------49b

2) THE SOURCE FOR THE THIRTY-NINE MELACHOS
QUESTION: The Gemara records two opinions regarding the source for the thirty-nine Melachos. Rebbi Chanina bar Chama says that we learn them from the labors performed in the Avodas ha'Mishkan. Rebbi Yonasan b'Rebbi Eliezer (in the name of Rebbi Shimon b'Rebbi Yosi ben Lekunya) says that the thirty-nine Melachos are derived from the thirty-nine times that the Torah mentions a form of the word "Melachah."
The Gemara implies that these two opinions argue with one another. However, RASHI explains that according to the first opinion, we learn from the Avodas ha'Mishkan exactly which Melachos are forbidden. The other opinion, though, merely gives a source for the number of Melachos that are forbidden. The two opinions complement each other. Why, then, does the Gemara imply that they argue?
ANSWER: RAV MENACHEM KASHER zt'l (Torah Sheleimah, Bereishis 39, #97) writes that the Yerushalmi (Shabbos 7:2) records this argument in a slightly different way, and it is cited in more detail in the Midrash (Mishnas Rebbi Eliezer, Parshah 20). There, the first opinion says that the thirty-nine Melachos correspond to the number of times the words "Melachah" and "Avodah" are mentioned in the description of the building of the Mishkan. According to the Yerushalmi, the first opinion in the Gemara is not only giving the source for what the Melachos are, but also for how many Melachos there are.
(See also Shabbos 70a, where the Beraisa suggests another source for the number of Melachos based on a verse which mentions the words "Eleh ha'Devarim" in connection to Shabbos. The Yerushalmi presents a similar source as well.)
3) WHERE ARE THE 39 WORDS OF "MELACHAH"?
QUESTION: The Gemara quotes several opinions for the source of the thirty-nine Melachos of Shabbos. The second opinion says that the Torah uses the word "Melachah" (or a construct thereof) thirty-nine times. The Yerushalmi says that the last "Melachah" of the count appears in Devarim 16:8, where the Torah commands us not to do Melachah on the seventh day of Pesach.
When we count the number of appearances of the word "Melachah" (or a construct thereof) in the Torah, we will find that the word actually appears 65 times (the word "Melachah" appears alone 25 times, and the word constructed with a prefix or suffix appears another 40 times; see Concordance). How, then, does the Gemara come up thirty-nine appearances of the word "Melachah"?
ANSWERS:
(a) RABEINU CHANANEL (cited by the RAMBAN here, and discussed at length by the RA'AVAN #350) explains that the Gemara counts the word "Melachah" only when it is written in the context of an act that is forbidden on Shabbos. (This assumption is implicit in the Gemara here, which relates the question of what each appearance of the word "Melachah" means, to the question of which words are included in the count). For this reason, the Gemara does not count the appearances of "Melachah" in the description of Creation in Bereishis, and it does not count the appearances of "Melachah" mentioned with regard to "Meleches Avodah" of Yom Tov (because the Melachos of Yom Tov do not include all of the Melachos that are forbidden on Shabbos). Similarly, the Gemara does not count the word "Melachah" in the verse, "For six days you shall do Melachah," because that verse does not command us to refrain from Melachah on Shabbos, but rather it commands us to do Melachah during the rest of the week. According to this criterion, the number of remaining appearances of the word "Melachah" is indeed thirty-nine.
Rabeinu Chananel, however, addresses only 61 of the 65 appearances of "Melachah."
(b) The TOSFOS YOM TOV (Shabbos 7:2) explains that included in the count are only appearances of the word "Melachah" that are not part of the commandment of "Lo Ta'aseh Melachah" -- "Do not do Melachah." The count, not including all of the commandments not to do Melachah, comes to a total of thirty-nine.
The problem with this answer is that the Yerushalmi says that a commandment that uses the word "Melachah" is included in the count (the Yerushalmi says that the last word in the count is the word in the verse that commands that Melachah not be done on the seventh day of Pesach). Also, the MAR'EH HA'PANIM on the Yerushalmi points out that the Tosfos Yom Tov missed a few occasions of the word "Melachah" and the count comes to more than 39, even without the commandments not to do Melachah.
(c) The MAR'EH HA'PANIM says that the word "Meleches" is not included in the count (because it is not a word by itself, but a dependent construct). This decreases the number by 19. He omits several other words from the count, because they do not refer to a Melachah that is forbidden on Shabbos.
However, the Torah Sheleimah (Bereishis 39, #97) points out that the Mar'eh ha'Panim does not account for all of the extra words. Another problem with his approach is that the text of the Gemara here, which says that "Meleches" is included in the count, must be emended.
(d) The Torah Sheleimah quotes the SEFER NETZACH YISRAEL (Rav Yisrael Segal, 1741) who says that the count does not include the appearance of the word "Melachah" in its raw form, with no prefix or suffix. This reduces the total of 65 to exactly 40 (from which our Gemara subtracts one). He, too, will have to emend the text of the Gemara here, which says that the word "Melachah" is included in the count. (See also Parasha Page, Pekudei 5757.)

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