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Parshah Halacha – Parshat Bo
A Historical and Halachic Background
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Parsha Halacha is underwritten by a grant from Dr. Stephen and Bella Brenner in loving memory of Stephen’s father, Shmuel Tzvi ben Pinchas, and Bella’s parents, Avraham ben Yitzchak and Leah bas HaRav Sholom Zev HaCohen
In the Torah portion of Bo, G-d gave Moshe the first mitzvah to command the Jewish people, that of sanctifying the new moon, as the Torah says, “The L-rd spoke to Moshe and to Aaron in the land of Egypt, saying, ‘This month shall be to you the head of the months. It shall be for you the first of the months of the year.’”
Regarding this verse the Rambam writes, “Our sages commented and said that, “The Holy One, blessed be He, showed Moshe an image of the moon in a vision of prophecy and told him, ‘When you see the moon like this, sanctify it.’” This mitzvah includes the concept of establishing the months through witnesses or through astronomical calculations and establishing leap years which keep the Jewish calendar aligned with the solar year.
Originally, the Sanhedrin (High Court) would calculate (based on their astronomical knowledge) when the new moon should be visible and would wait for witnesses to come and testify that they saw the new moon. Only then would the Court declare that day to be Rosh Chodesh, the first day of the coming month. If witnesses showed up on a day when, astronomically, the new moon was not yet visible, the Court would not accept their testimony as they knew the witnesses were either mistaken or lying. In addition, through their calculations, the Court knew where in the sky the moon was going to appear, what direction it would face, and how thick or thin it would be. This knowledge would aid them in weeding out unreliable witnesses.
Our teacher Moshe relayed a tradition that he received from G-d at Mount Sinai that when the Sanhedrin would no longer function, “the monthly calendar will be established according to the fixed calendar that we follow now, and the sighting of the moon will be of no consequence.”
Yom Tov Sheini
During the time that months were established by the Sanhedrin, the Jews who lived far away from the Sanhedrin were unsure as to the correct day to observe the festivals since the month preceding those festivals may have had either 29 or 30 days. As such, they would observe two days for each day of Yom Tov (festival) to cover both possibilities. The second day is known as Yom Tov Sheini shel Galuyot, the second day of Yom Tov observed in the Diaspora.
The Talmud says that, although we now know the exact date of every holiday based on the calendar system, we should continue to observe two days for each Yom Tov in the Diaspora. The reason for this is that an evil government might make a decree which would cause Yom Tov not to be observed properly.
Rashi explains that, as a result of religious oppression, the Jewish people might cease studying Torah properly and thus might forget how to make the necessary calculations to establish the calendar. (Although this can also happen in the land of Israel, they did not wish to establish a new observance based on this concern, whereas in the Diaspora, where two days of Yom Tov were already being observed, the sages instructed that this practice continue.)
This article will explore the development of the observance of Yom Tov Sheinibefore, during, and after the Talmudic era.
Although the simple understanding is that the observance of Yom Tov Sheinididn’t begin until the Jews went into exile from the Land of Israel (and thus didn’t know when to observe Yom Tov), some say that the concept of Yom Tov Sheini actually began much earlier.
There are opinions that the early prophets (perhaps as early as the time of Yehoshua Bin Nun) instructed the Jews that if they are in the Diaspora (outside the Land of Israel) they should observe two days of Yom Tov. They did not reveal the reason for this instruction. Since they may have had secret reasons for this law, we must observe it even after the calendar was established.
Observed in Israel
The halacha states that if the greatest sage of Israel leaves the Land of Israel and there is no one as great as him left there, he may establish the months and years from the Diaspora. There are several times that this occurred in our history. The Chatam Sofer writes that during those times it seems that the Jews in Israel (and not those in the Diaspora) would celebrate the second day of Yom Tov as they did not know which the correct day was to celebrate.
Messages of Fire
There was a period when the date of Rosh Chodesh was relayed to the Jews of Babylonia by designated people who would signal to each other by waving fires from a series of mountaintops. The Rambam writes that during this time, the Babylonian Jews did not need to observe the second day of Yom Tov since they knew exactly when Yom Tov occurred.
Messengers to the Diaspora
The system of sending messages by signals of fire was halted by the sages when the Baytusim corrupted the system by deliberately sending false signals. (The Baytusim were a sect of Jews who didn’t believe in the Oral Torah and wanted to meddle with the Jewish calendar to suit their beliefs.) Instead, they made a new system. After establishing the new month, the Sanhedrin would send out messengers to inform the Jews in exile of the date of Rosh Chodesh so they could observe the holidays on the proper day. Those who lived too far for the messengers to reach them before the festival would observe a second day of Yom Tov as they were not sure which day was the actual holiday.
Some say that during this time the observance of the second day of Yom Tov was mandated based on the principle that one must be strict on a doubtful Torah obligation. Thus, each of the two days was possibly a festival by Biblical law and must therefore be observed as such. At that time, because both days of Yom Tov were possibly the Biblical holiday, the laws of the second day of Yom Tov was precisely the same as those of the first day of Yom Tov. Whereas nowadays, when the second day of Yom Tov is of Rabbinic origin, it has a few leniencies over the first day.
Others say that even during that time, it was only necessary by Torah law to observe the first day of Yom Tov since in almost every year, both Elul and Adar have 29 days. Thus, based on the principal of following the majority, the first day of Yom Tov was the day most likely to be Yom Tov and thus the one obligatory by Torah law. The rabbis, however, mandated that the second day of Yom Tov be observed in case Yom Tov actually fell out on that day. According to this opinion, even in that era, there were certain leniencies on the second day of Yom that did not apply on the first day.
During this time there were some sages in the Diaspora who knew how to calculate the lunar cycles and were therefore able to know when Rosh Chodesh was likely to be. They nevertheless would keep two days of Yom Tov because of the possibility that the witnesses had not been accepted by the Sanhedrin.
The Holiday of Shavuot
Even in the era when Diaspora Jews were dependent on the messengers of the Sanhedrin to know the date of Rosh Chodesh, the Diaspora Jews were never in doubt about the proper date for Shavuot. This is because Shavu’ot is always 50 days after the second day of Pesach. Thus, once the date of Rosh Chodesh Nissan was known, the date of Shavuot could be calculated – 66 days later. At that time, there were no Jews living more than 66 days of travel from Israel. Despite this, the rabbis established that Diaspora Jewry observe two days of the holiday of Shavuot to establish uniformity in the observance of Yom Tov and to ensure that the second day of Yom Tov would always be treated with respect. The Chatam Sofer writes that, based on this, the observance of the second day of Shavuot is even more stringent than that of the other second days of Yom Tov since it was enacted by the rabbis and was never observed merely as a doubt. The Lubavitcher Rebbe adds that this can have halachic ramifications in some circumstances. In addition, it teaches us a lesson that the giving of the Torah (which happened on the holiday of Shavu’ot) should dispel any doubts (just as the second day of this Yom Tov is not observed because of a doubt) and give one the strength to serve G-d with certainty.
Even during the era of the messengers, most Jews did not observe Yom Kippur for two days as this would entail 49 hours of consecutive fasting which would prove very difficult if not downright dangerous. They would therefore assume that the month of Elul had only one day of Rosh Chodesh (which was almost always the case) and fast only on the first day of Yom Kippur. (But see below, note 33.)
When was the Calendar System Made?
Today’s calendar system by which we calculate all of the months and years was made by Hillel, the son of Rabbi Yehudah Nesi’a.
The Ra’ah (Rabbi Aharon ben Yosef HaLevi of 13th-century Spain) wrotethat Hillel made the calendar in the time of Rav Zeira who was a contemporary of Rav Yosef. There are several passages in the Talmud that support this view.
On the other hand, the Rambam wrote that the calendar was created at the end of the Talmudic era and that at the time of Abaye and Rava, the Sanhedrin was still establishing the months based on testimony. (Abaye was a student of Rav Yosef.) This view can also draw support from several passages in the Talmud.
In the Messianic Era
The Chatam Sofer writes that when Moshiach comes, the Sanhedrin will abolish the fixed calendar and go back to sanctifying Rosh Chodesh on a monthly basis, based on the testimony of witnesses who will see the new moon. As such, he writes, even though the holiness of the Land of Israel will spread to many other countries, all of the areas that are distant from Israel will have to continue to observe two days of Yom Tov as they will not know which is the correct day.
It is possible that since nowadays we have instant communication and the entire world can find out in seconds as to when Rosh Chodesh was established, it will no longer be necessary to observe the second day of Yom Tov. Others say that even then this day will continue to be observed.
Eliyahu HaNavi and Moshiach will certainly clarify all of this for us. May they arrive speedily in our days!
 Exodus 12:1 and 2
 Laws of Kiddush HaChodesh, 1:1
 Mechilta D’Rashbi on the verse; see also Menachot 29a.
 Sefer HaChinuch, Mitvzah 4
 Rambam, Laws of Kiddush HaChodesh 1:6 and 2:4
 The Sanhedrin can only function when the rabbis had Smicha – ordination that was received in a direct link from our teacher Moshe. When this ordination ceased in the fifth Century (approximately), the Sanhedrin was disbanded.
 Ibid 5:2
 Beitzah 4b
 Mishnah Berurah 496:1
 In preparing this article I used the book Yom Tov Sheini Kehilchato by Rabbi Yerachmiel Fried (Jerusalem 1998) as well as several sources provided by Rabbi Shmuel Roth of Benei Berak.
 Otzar HaGe’onim on Beitzah 4b in the name of Rabbi Sa’adiah Gaon, quoted in Torah Shleima vol. 13, chapter 11
 See Likutei Torah, Shemini Atzeret, 92c for a spiritual explanation for this matter.
 See Rambam, ibid, 1:8
· Yevamot 122a that Rabbi Akiva once went to Naharda’a (in Babylonia) to establish the new month.
· Brachot 63a says that for some time, Rabbi Chanina, the nephew of Rabbi Yehoshua, was establishing the months while in Babylonia.
· In addition, it would seem that during the 70 years of the Babylonian exile – between the first and second Bait HaMikdash – they established the months (and years) in Babylonia since there was no one in the land of Israel who could do it.
 Responsa Y.D. 252 D.H. Venahirna. The Chatam Sofer is quoting a conversation he had with the Noda BiYehudah.
 Rosh HaShana 22b
 Hilchot Kiddush HaChodesh 3:8 and 11
 See Rashbam on Bava Batra 115b D.H. Im, based on Avot DeRabi Natan 5:2
 See Rambam, Hilchot Kiddush HaChodesh 3:9 as to which months the messengers were sent to report on.
 Tzlach (by Rabbi Yechezkel Landau) on the beginning of Beitzah 6b
 See O.C. 496:2
 See Torat Refael by Rabbi Refael Shapiro of Volozhyn (1837 – 1921), O.C. vol. 2, Siman 101 D.H. Omnam HaRashbatz, in explanation of the opinion of the Rosh.
 Chidushei Chatam Sofer al HaShas, Beitzah 4b D.H. Vehashta Deyadinan
 Rambam, ibid, 3:12
 Responsa O.C. end of Siman 145
 Sha’arei HaMo’adim, Shavuot, page 325 from Torat Menachem 5710 page 90
 Shulchan Aruch HaRav 624:10. See Ohr Same’ach on Hilchot Kiddush HaChodesh 3;11
 On Beitzah 4b
 See Chullin 46a
 The following sources are quoted by Rabbi Chaim Kaniefsky in Shekel HaKodesh on Hilchot Kidush HaChodesh 5:3, D.H. Ad Yemei Abaye:
· Pesachim 51a: Rav Safra said, “Since we know the cycle of the moon, why do we need to keep two days of Yom Tov?” Rav Safra passed away during the lifetime of Abaye (see Moed Katan 25a), yet he said that they knew the lunar cycle. Presumably this means that they had a calendar system in place. (But see there Tosfos D.H. Kegon Ana.)
· Beitzah 4b: Rav Zeira said that he knew the established months.
 Hilchot Kiddush HaChodesh 5:3
· Rosh HaShana 21a that Rava fasted on two days for Yom Kippur as he was unsure of the correct day.
· Sanhedrin 12a states that a pair of Torah scholars came from Tiberias and informed Rava (in code due to the decrees made by the government at that time) that the upcoming year would be a leap year.
· Ta’anit 29b Abaye cursed one who washed his clothes on Tisha B’av that coincided with Friday. When there is a calendar system, Tisha B’av cannot coincide with Friday.
 Responsa O.C. end of Siman 145
 See Gittin 8a
 The Chatam Sofer surmises that this day will be called Yom Tov Sheini shel Ge’ulot(instead of “Galut”) – the second day of Yom Tov of the Redemption (instead of “Diaspora”).
 Rav Elyashiv, quoted in the Dirshu edition of the Mishna Berurah 496, note 3
 Rabbi Shlomo Zalman Auerbach, cited in Yom Tov Sheini KeHalacha, page 15, note 3
Wishing you a Shabbat Shalom UMevorach!