1) AN EGG ON THE SECOND DAY OF ROSH HASHANAH: "HA LAN V'HA LEHU"
QUESTION: The Gemara says that after the enactment of Raban Yochanan ben Zakai, an egg laid on the second day of Rosh Hashanah should be permitted. Raban Yochanan ben Zakai's enactment reinstated the practice that witnesses who come to testify about the sighting of the new moon are accepted by Beis Din all day long, even after the time of Minchah. The original enactment of the Rabanan required two days of Rosh Hashanah because of the possibility that witnesses might come after Minchah time, in which case their testimony would be accepted only on the following day and both days would be declared as Rosh Hashanah, and thus the two days of Rosh Hashanah had one long Kedushah. The only reason why two days of Rosh Hashanah are observed now that the original enactment is no longer in effect is because of the doubt which day is really the first of the month.
The Gemara explains that when Rav and Shmuel said that an egg laid on the second day of Rosh Hashanah is prohibited nowadays even after Raban Yochanan ben Zakai's enactment, they were referring "to us" and not "to them." Rashi explains that "to them" refers to the people in Eretz Yisrael. Since they did not observe two days of Rosh Hashanah every year but only when the witnesses arrived after Minchah time, nowadays -- when witnesses are accepted after Minchah time -- there is never two days of Rosh Hashanah in Eretz Yisrael. In contrast, the people in Bavel (outside of Eretz Yisrael) always observed two days of Rosh Hashanah out of doubt about which day was declared the new month in Yerushalayim. Those two days retain the status which they had during the time of the original enactment (not to accept witnesses after Minchah time), and thus the two days of Rosh Hashanah have one long Kedushah. Therefore, an egg laid on the first day is prohibited on both days.
Why does the Gemara differentiate only between the people of Bavel and the people of Eretz Yisrael? Even in Eretz Yisrael, the people in most places outside of Yerushalayim were required to observe two days of Rosh Hashanah because they did not know exactly when Beis Din in Yerushalayim had declared the new month. Beis Din could not inform any of the distant places because they were beyond the limit (Techum) which one may travel on Yom Tov. Both before and after the enactment not to accept witnesses after Minchah time, most places in Eretz Yisrael observed two days of Rosh Hashanah. The two days of Rosh Hashanah should have one long Kedushah in those places, and an egg born on the first day should be prohibited on the second day as well.
(a) The BA'AL HA'ME'OR and the ME'IRI indeed explain that "to them" refers not to the people in Eretz Yisrael but to the people in Yerushalayim, within the Techum of Beis Din.
Rashi, however, mentions nothing about Yerushalayim. He differentiates only between the people in Bavel and the people in Eretz Yisrael, implying that all of the people in Eretz Yisrael had the same practice regardless of where in Eretz Yisrael they lived. How could they all have had the same practice, if the places outside of the Techum of Beis Din were required to observe two days of Rosh Hashanah just like the people in Bavel, while the places near Beis Din observed only one day?
(b) Perhaps RASHI understands that since it is possible to declare the new month in any part of Eretz Yisrael, every city in Eretz Yisrael has the status of the city in which Beis Din declares the new month (as the ME'IRI writes in reference to another matter; see below, Insights to Beitzah 5:3). After the enactment of Raban Yochanan ben Zakai, the place in which Beis Din would declare the new month would have two days of Rosh Hashanah with two Kedushos. Therefore, in the rest of Eretz Yisrael as well the two days of Rosh Hashanah would not be one long Kedushah but two separate Kedushos.
2) HALACHAH: ANNULLING AN ENACTMENT OF BEIS DIN
OPINIONS: The Gemara states that an enactment instituted by Beis Din may be rescinded only through the annulment of Beis Din ("Davar she'b'Minyan Tzarich Minyan Acher l'Hatiro"). Without the annulment, the enactment will not be canceled even when the cause for the enactment is no longer extant. When does this principle apply, and to what extent does it apply?
(a) RASHI in Sanhedrin (59b) writes that this rule applies even when the original enactment was instituted for a limited period of time. Even after the time has passed, the enactment remains in force until a Beis Din annuls it. The enactment does not become annulled by itself even though it was made contingent on a specific period of time.
Rashi proves this from the source for this rule quoted by the Gemara. Hash-m commanded the Jewish people to separate from their spouses for three days before the Giving of the Torah. Even though that commandment was limited to only three days, it needed an annulment from Hash-m in order to permit the men to return to their wives.
The AGUDAH cites in the name of Rashi that this stringency applies even in the case of a Cherem (excommunication) made by Beis Din against a certain act. Even if the Cherem was limited to a certain period of time, the act remains forbidden by the Cherem even after the time period has passed.
(b) The other Rishonim reject this approach and argue that Hash-m did not command the men to separate from their wives for three days, but rather to separate from their wives in honor of the event that was to occur after three days. Thus, the commandment was not bound by any specific amount of time. TOSFOS in Sanhedrin (59b) writes that Rashi himself rescinded his opinion. Indeed, Rashi here (5b, DH Hachi ka'Amar) and in the Chumash (Shemos 19:15) explains that this is the meaning of "for three days."
Therefore, the Rishonim write that an enactment limited to a specific amount of time does not need a Beis Din to annul it. It becomes annulled by itself when the time passes, both in the case of an enactment and in the case of a Cherem. A special annulment is necessary only when the wording of the original enactment did not specify that the enactment should become annulled if circumstances change, or when the wording did not specify that the enactment was made for a certain reason.
(c) The SHITAH MEKUBETZES differentiates between an enactment made to prohibit something (Takanas Isur) and an enactment of Cherem. A Cherem, because of its severity, requires the annulment of Beis Din even if it was limited to a specific amount of time. The Shitah Mekubetzes proves this from the Gemara in Makos (11b) which says that a "conditional Cherem" ("Cherem Al Tenai" -- a Cherem against a person that takes effect on condition that he does or does not do a certain thing) must be annulled by Beis Din even if the condition is not fulfilled. The Gemara there relates that Yehudah accepted upon himself a Cherem that he would bring Binyamin back to his father (that is, if he would fail to bring Binyamin back, the Cherem would take effect). Even though he did bring Binyamin back, the Cherem took effect (and the bones of Yehudah rolled around in the coffin).
Other Rishonim refute the proof from Yehudah. The RITVA in Makos writes that Yehudah did not completely fulfill the condition upon which the Cherem was contingent. He did not bring Binyamin all the way back to his father; he merely left him with Yosef until his father came to Mitzrayim (as the PANE'ACH RAZA in Bereishis 45:23 writes), and therefore the Cherem remained in force. Had Yehudah completely fulfilled the condition, the Cherem would have been annulled automatically without the need for Beis Din to annul it.
HALACHAH: It is not clear from the Poskim to what extent a decree needs a Beis Din in order to be annulled. The DARCHEI MOSHE (YD 231) seems to rule stringently, like Rashi, that even a Cherem or Takanah which was enacted for a specific amount of time needs the annulment of Beis Din. The SHULCHAN ARUCH (YD 334:13, 27) seems to rule stringently even in the case of a Cherem upon an individual, which, he rules, will not become annulled by itself even after its stated time period has passed.
3) HALACHAH: HOW MANY DAYS OF ROSH HASHANAH ARE OBSERVED IN ERETZ YISRAEL
OPINIONS: During the times of the Gemara when Beis Din declared the new month based on the testimony of witnesses who saw the new moon, the people in areas outside of the place of Beis Din needed to observe two days of Rosh Hashanah. Since Beis Din could not notify them immediately about the declaration of the new month (since they were beyond the Techum of Beis Din), they had a doubt as to which day was declared as the new month. Nowadays a set calendar is used and the day of the new month is determined by calculation. The basis for this practice is the Halachah l'Moshe mi'Sinai which teaches that when there is no Beis Din to declare the new month, a set calendar is to be used. Accordingly, the exact day of Rosh Hashanah is known well in advance and there is no doubt that the following day might be Rosh Hashanah.
In all areas outside of Eretz Yisrael, Jews observe two days of Rosh Hashanah because of the principle, "Minhag Avoseinu b'Yadeinu" (4b): the Rabanan decreed that we follow the practice of our fathers who observed two days of Rosh Hashanah in Chutz la'Aretz during the times when Beis Din in Yerushalayim sanctified the first day of the new month. As the Gemara (4b) explains, the Rabanan instituted that even in the times when Beis Din in Yerushalayim no longer establishes the new month, the people in Chutz la'Aretz must observe the "Minhag Avoseihem b'Yedeihem" lest the burden of foreign subjugation cause the people to forget the proper way to calculate the new month.
In the place where Beis Din convened, there was never a practice to observe two days of Rosh Hashanah because the day of the establishment of the new month was known immediately. Accordingly, there should be grounds for the people in Yerushalayim today to observe only one day of Rosh Hashanah. What is the reason for the practice to observe two days of Rosh Hashanah even in Yerushalayim?
Similarly, what is the reason for the practice to observe two days of Rosh Hashanah in other cities in Eretz Yisrael? On one hand, in the times of Beis Din the people in other cities in Eretz Yisrael observed two days of Rosh Hashanah because they did not know when Beis Din sanctified the new month. On the other hand, nowadays the exact day of Rosh Hashanah is known because of the set calendar, and the Gemara says that the enactment to observe "Minhag Avoseinu b'Yadeinu" applies only in Chutz la'Aretz but not in Eretz Yisrael, and thus all of the people in Eretz Yisrael should observe only one day of Rosh Hashanah.
How many days of Rosh Hashanah should be observed in Eretz Yisrael and in the place of Beis Din?
(a) The BA'AL HA'ME'OR records in the name of the TESHUVOS HA'GE'ONIM that the people in Eretz Yisrael sent a question to the Ge'onim inquiring whether they were correct in their practice of observing only one day of Rosh Hashanah. The Ge'onim replied simply, "Minhag Avoseichem b'Yedeichem," and that they are correct in observing only one day since that was the practice of their fathers. The Ba'al ha'Me'or writes that nowadays (in his time), although the people in Eretz Yisrael observe two days of Rosh Hashanah, they do so only in error (he describes the source of the error).
The words of the Ba'al ha'Me'or are difficult to understand. Why should all of Eretz Yisrael observe only one day? During the times that Beis Din sanctified the new month based on the testimony of witnesses, the people in distant cities in Eretz Yisrael certainly observed two days of Rosh Hashanah due to the doubt about exactly which day Beis Din sanctified. Accordingly, the people in those places in Eretz Yisrael now should also observe two days, like the people in Chutz la'Aretz.
The ME'IRI explains that in Eretz Yisrael the Rabanan were not concerned that foreign subjugation would cause the people to forget how to calculate the new month. Therefore, the Rabanan did not institute the practice of following the Minhag of their fathers in Eretz Yisrael. Only in Chutz la'Aretz is there a fear that the people will forget how to calculate the new month.
The Me'iri adds that there is reason for all of Eretz Yisrael to follow the status of the place of Beis Din (as described earlier; see Insights to Beitzah 5:1:b). Since it was possible for Beis Din in any part of Eretz Yisrael to declare the new month, every city in Eretz Yisrael has the status of the city in which Beis Din declared the new month. Therefore, every city in Eretz Yisrael may follow the practice of the city in which Beis Din established the new month.
(b) The ME'IRI himself agrees with the Ba'al ha'Me'or that in Yerushalayim the people should observe only one day of Rosh Hashanah because there never was a "Minhag Avoseinu" in Yerushalayim to observe two days. He argues, however, that in the rest of Eretz Yisrael the people should observe two days because "Minhag Avoseinu" does apply.
(c) The RAMBAN (in Milchamos) strongly opposes the view of the Ba'al ha'Me'or. He writes that in Eretz Yisrael the people should observe two days of Rosh Hashanah. He explains that the Ba'al ha'Me'or misunderstood the responsum of the Ge'onim. When they replied that the people in Eretz Yisrael should observe "the Minhag of their fathers," they were not referring to the Minhag to observe one day of Rosh Hashanah, but rather to the Minhag to observe two days of Rosh Hashanah in Eretz Yisrael during the times when Beis Din in Yerushalayim sanctified the new month based on the testimony of witnesses.
The Ramban does not differentiate between Yerushalayim and the rest of Eretz Yisrael in this matter. The "Minhag Avoseihem" to observe two days of Rosh Hashanah applies to Yerushalayim as well.
Why, though, should the people observe two days of Rosh Hashanah even in Yerushalayim nowadays, when there never was a practice to observe two days there in the times of Beis Din?
Perhaps the Ramban applies a reasoning similar to that expressed by the Me'iri (but uses it to arrive at the opposite conclusion). Since it was possible for Beis Din in any city in Eretz Yisrael to declare the new month, the city of Yerushalayim cannot have the exclusive practice to observe only one day of Rosh Hashanah; there is no single place which can be said to observe only one day. Therefore, all of Eretz Yisrael observes two days, including Yerushalayim.
Another reason for why the principle of "Minhag Avoseihem" applies even in Yerushalayim is because even there two days of Rosh Hashanah were sometimes observed. When witnesses did not arrive on the first day, two days of Rosh Hashanah would be observed. (According to Rashi here, two days would be observed when witnesses came after Minchah on the first day, even after the enactment of Raban Yochanan ben Zakai.) Even though witnesses usually came early on the first day and only one day of Rosh Hashanah was observed, nevertheless since it occasionally happened that the witnesses came later and two days were observed, it is considered the "Minhag Avoseihem" to observe two days of Rosh Hashanah even in Yerushalayim.