1) BEIN HA'SHEMASHOS
QUESTION: According to Rebbi Yehudah, the duration of Bein ha'Shemashos (from Sheki'ah until Tzeis ha'Kochavim, when three stars appear) is either 2/3 (Rav Yosef) or 3/4 (Rabah) of the time that it takes to walk one Mil. However, the Gemara in Pesachim (94a) records a discussion concerning how long it takes for the sun to go through the "thickness of the firmament" (that is, for its light to disappear). The Gemara says that it takes from sunset (Sheki'ah) until the stars appear (Tzeis ha'Kochavim) for the sun's light to disappear. Rebbi Yehudah there says that the period from Sheki'ah to Tzeis ha'Kochavim is the amount of time that it takes to walk four Mil!
How are we to reconcile this contradiction in the words of Rebbi Yehudah? In Pesachim, he says that the duration of Bein ha'Shemashos is four Mil, but here in Shabbos he says that it lasts only 2/3 or 3/4 of a Mil!
(a) TOSFOS (DH Trei) explains that there is a difference between the Gemara here and the Gemara in Pesachim. When the Gemara in Pesachim says "mi'Sheki'as ha'Chamah" (and not "mi'Shetishka ha'Chamah," as it says here), it is referring to the moment that the sun disappears from our vision. At that moment, though, it is still journeying through the firmament. When the sun reaches a certain point in the thickness of the firmament, its light begins to disappear. This is referred to as "mi'Shetishka ha'Chamah." Shortly afterwards, its light disappears altogether and three stars can be seen.
In summary, the order of events is: 1. the sun disappears, 2. a period of 3 1/4 (or 3 1/3 according to Rav Yosef) Mil passes, after which time the light of the sun begins to totally disappear (this is the start of the Beis ha'Shemashos discussed here in Shabbos), and then 3. a period of 3/4 Mil (or 2/3 according to Rav Yosef) passes, after which the sun has completely disappeared and the stars appear. This is the view of RABEINU TAM.
(b) The VILNA GA'ON (in SHENOS ELIYAHU, beginning of Maseches Berachos, and in BI'UR HA'GRA OC 235 and 261) explains that both here and in Pesachim the times mentioned (3/4 Mil and 4 Mil) start from the time that the sun completely disappears from our view. However, the Gemara in Pesachim is discussing a different Tzeis ha'Kochavim than our Gemara (and not a different Sheki'as ha'Chamah, as Rabeinu Tam suggests). In Pesachim, "Tzeis ha'Kochavim" refers to the time at which every last ray of light disappears from the sky (which occurs four Mil after sunset), and all of the stars can be seen. In the Gemara here, "Tzeis ha'Kochavim" refers to the time at which three medium-size stars can be seen, which is the Halachic definition of nightfall. (The Gemara in Pesachim, in contrast, is an Agadic discussion and is not referring to the Halachic Tzeis ha'Kochavim.)
2) MOSHE RABEINU'S SIN AND MIRIAM'S WELL
AGADAH: The Gemara states that the waters of the well of Miriam (Be'er Miriam) were valid for Tevilah. Based on this statement, The ROGATCHOVER GA'ON (in SHE'EILOS U'TESHUVOS TZAFNAS PANE'ACH 119:7) explains the nature of the sin of Moshe Rabeinu, when he hit the rock to bring forth water for the Jewish people. Why was Moshe Rabeinu punished for hitting the rock, when Hash-m had commanded him to hit it?
When Moshe Rabeinu took the stick and hit the rock, the verse states, "... as He commanded him (Asher Tzivahu)" (Bamidbar 20:9). In other places, though, when Moshe fulfills the dictates of Hash-m, the verse says, "As Hash-m commanded him (Asher Tzivahu Hash-m)." This subtle change indicates that when Hash-m commanded Moshe to take the stick, Moshe acted according to his interpretation of Hash-m's command, which was slightly different from what Hash-m had actually intended. Hash-m told Moshe to take "the stick" (Bamidbar 20:8). Moshe, in his modesty, thought that Hash-m meant Aharon's stick, the one that had been placed in the Sanctuary from the time that it miraculously sprouted almonds. The verse states that Moshe took a stick from "before Hash-m" (Bamidbar 20:9), that is, from within the Sanctuary -- Aharon's stick. That was the stick he used to hit the rock to bring forth water.
In the Mishnah in Mikva'os (5:5), Rebbi Yosi says that a Mikvah formed by objects (such as lining up sticks around a Mikvah to direct water into it) that can become Tamei is invalid. Since sticks can become Tamei, a Mikvah made with sticks is invalid and cannot be used for Tevilah. When the Jews were traveling through the wilderness, there were no valid Mikva'os for them to use (see Tosfos to Bechoros 56a). The only water in which they could immerse themselves was in the water that came forth from Miriam's well, as the Gemara here says.
Had Moshe struck the rock with his own stick -- which was made out of sapphire (Shemos Rabah 6), a stone that cannot become Tamei -- the water that came from the rock would have been valid for Tevilah. Since he hit the rock with Aharon's stick which was made of wood and could become Tamei, the waters of the rock were invalid for Tevilah, because they were brought about by an object that could become Tamei. As a result, for the last year of their sojourn in the wilderness, the Jewish women were unable to immerse themselves. This caused considerable stress in the relationship between husband and wife, which is why those waters were called "Mei Merivah" -- "the Waters of Strife"!

35b----------------------------------------35b

3) HALACHAH: DOING "MELACHAH" AFTER LIGHTING THE SHABBOS CANDLES
OPINIONS: In the Beraisa, Rebbi Nasan says that we blow six Shofar blasts on Erev Shabbos. One of the blasts (the third) tells people to light the Shabbos candles.
Is one permitted to do Melachah after he has lit the Shabbos candles? The Gemara in Yoma (81b) says that when a person recites the blessing "Shehecheyanu" to herald the arrival of Yom Kipur, he becomes prohibited from doing Melachah, and all of the prohibitions of Yom Kipur take effect, even though the sun has not yet set. Does the same Halachah apply to one who lights the Shabbos candles before Shabbos? Does Melachah become forbidden once he has lit the candles?
(a) The RAMBAN (Shabbos 23b) writes that the two cases are not comparable, for several reasons:
1. When one recites "Shehecheyanu" before Yom Kipur, he demonstrates that his intention is to accept upon himself the sanctity of the day. With regard to Shabbos, one's lighting of the candles does not necessarily show that he wants to accept upon himself the sanctity of Shabbos. Rather, since lighting on Shabbos itself is forbidden, he is merely trying to finish lighting the candles early enough so that he can move on to the other preparations for Shabbos.
2. Second, lighting the candles is itself a Melachah, and by lighting them one shows that it is not Shabbos. Therefore, the act of lighting the candles cannot serve to usher in Shabbos the way that the blessing of "Shehecheyanu" serves to usher in Yom Kipur.
3. The Ramban finds support for his opinion in the Gemara here, which says that the third blast of the Shofar indicates the time to light the Shabbos candles. The Gemara explains that time was given before the blowing of the fourth blast to allow the person who just lit Shabbos candles to go "roast a small fish or affix dough to the inside of the oven." The Gemara clearly says that one is permitted to do Melachah after he lights the Shabbos candles. (RASHI 35b, DH Madbik, also says that this time was given for them to actually place the dough in the oven.)
Therefore, the Ramban concludes that on Shabbos Chanukah, a person should light the Shabbos candles before he lights the Chanukah candles, because the Shabbos candles are more important (as the Gemara on 23b states), and one is permitted to do Melachah after lighting them.
(b) The RAN and BEHAG disagree with the Ramban. They base their view on three points:
1. The lighting of the Shabbos candles marks the beginning of Shabbos. Although the lighting itself is a Melachah, since it is a Mitzvah that is done for the sake of Shabbos, it is considered the beginning of the cessation from Melachah.
2. When the Gemara says that there was a pause between the third and fourth Shofar blasts so that people could roast fish or affix dough to the ovens after lighting the Shabbos candles, it means only that this amount of time was given as a pause between the blasts, but not that it was actually permitted for them to do Melachah after lighting the Shabbos candles.
3. The Beraisa mentions that "they would light the Shabbos candles" after it lists all of the other tasks that people would do first. This implies that the lighting of the candles is the last Melachah to be done before Shabbos. This is especially evident from the Mishnah earlier (34a), which states that one is permitted to do Hatmanah during Bein ha'Shemashos. Accordingly, the Beraisa here should list Hatmanah after it lists the lighting of the Shabbos candles (because lighting the candles is forbidden during Bein ha'Shemashos, since it is a Melachah d'Oraisa, and Safek d'Oraisa l'Chumra). It must be that the Rabanan decreed that the lighting of the candles is to be the last Melachah done before Shabbos. Similarly, the Beraisa says that according to Rebbi Yehudah, the third Shofar blast signaled to everyone to remove their Tefilin, and the fourth blast signaled the time to light the candles. Since wearing Tefilin is a Mitzvah, removing the Tefilin should have been done after lighting the candles. It must be that once the Shabbos candles have been lit, the sanctity of Shabbos takes effect and Melachah is forbidden.
HALACHAH: The SHULCHAN ARUCH (OC 263:10) cites both opinions and writes that we follow the second opinion (the more stringent one). The REMA, however, notes that one may stipulate before lighting the candles that one does not intend to accept Shabbos at that moment. According to the opinions that the Rema cites, the ruling that lighting the Shabbos candles serves as one's acceptance of Shabbos is only a custom, based on the fact that the woman's unexpressed intention is usually to accept Shabbos at that time. She may, however, stipulate not to accept Shabbos. (In contrast, according to the Ran, who says that the Rabanan decreed that when one lights the candles, she accepts Shabbos, stipulating not to accept Shabbos does not help.)
The MISHNAH BERURAH (263:42) points out that when a man lights the Shabbos candles, the lighting does not serve as his acceptance of Shabbos. (This seems to be in accordance with the ruling of the Rema, who maintains that it is only a custom, and not a decree, that a woman's acceptance of Shabbos is dependent on lighting the candles. The custom was accepted by women, but not by men.)