Sanctified For Now And Thereafter
“In Front of the Sun or Behind It?”
(Rosh Hashana 23b)
The Mishna on this daf is central to any discussion of the role of Beis Din and its power to set and sanctify a new month [moon] as it describes at length how they [Beis Din] would inaugurate the new month based on the testimony of witnesses who sighted the new moon and how they would carefully cross-examine the witnesses. Sadly, today, we no longer have the Beis HaMikdash and we no longer have a Beis Din authorized to receive testimony to declare a new month. Instead, we make use of a calendar in which the months and years were standardized, based on a variety of halachic principles (see Rambam, Hilchos Kiddush HaChodesh chapter 6-8 and Tur O.C. 427-428). Based on the principles known by our Sages, we can foretell when the new moon will appear,
A Fixed Calendar
When did this calendar first come into use? The Gemara does not explicitly tell us. The Rashba (Teshuvos 4:254) writes: “We have a tradition that this system was instituted by Hillel, the son of Rabbeinu HaKodesh (Rebbe Yehuda HaNassi). However, I know of no source for this tradition.” Apparently there must be a misprint in our version of the Rashba, since the Hillel to whom he refers to was not the son of Rebbe Yehuda HaNassi. He was a descendant of Rebbe Yehuda HaNassi, who served as Nassi many generations later. (Teshuvos Tashbatz, Machon Yerushalayim, p. 413, footnote 34). The position of Nassi was held by Hillel the Elder, Rebbe Yehuda HaNassi, and the later Hillel who developed the calendar. The Nassi’im were descendants of David HaMelech, who held both political and spiritual leadership over the Jewish people in Eretz Yisroel, even after the Kings of Yehuda were dethroned.
Earliest Known Attribution
The earliest source we can find in which Hillel is attributed with developing the calendar, is from the writings of R’ Avraham ben R’ Chiya HaNassi, one of the early Rishonim, who is known mostly for his sefarim on astronomy. In one of his works, Sefer Ha’Ibbur (3:7), he cites Rav Hai Gaon, who writes that the Jewish calendar was developed by Hillel in the year 4119 (1655 years ago). The Ramban (Sefer HaZechus on Gittin, 36a) writes the same. He explains that at that time the Sanhedrin in Eretz Yisroel was disbanded, and there were no longer any judges authorized to inaugurate the new month based on the testimony of witnesses. Therefore, Hillel devised a calendar, which would be used by all future generations until the Sanhedrin would be restored.
The Rambam (Hilchos Kiddush HaChodesh 5:3) writes that this coincided with the end of the era of Abaye and Rava (who passed away in the years 4098 and 4113, according to the Iggeres Rav Sherira Gaon). We find in the Gemara that during the time of Abaye and Rava, the new month was still inaugurated based on the testimony of witnesses. In Rosh Hashana (21a) we find that it happened one year that Rava was uncertain which day was Yom Kippur. In Taanis (29b), we find that Tisha B’Av occurred on erev Shabbos during the time of Abaye (an occurrence impossible according to Hillel’s calendar – see Or Samei’ach on the Rambam, ibid). Soon after, the calendar came into use.
On Whose Authority
What is the authority of Hillel’s calendar? The first mitzvah instructed Moshe Rabbeinu was the mitzvah of Kiddush HaChodesh, by which Beis Din inaugurates the new month on the basis of the appearance of the moon, from which the dates for the Yomim Tovim of that month are determined. In other words, the Torah grants authority to Beis Din to determine the dates for Rosh Chodesh and Yom Tov. What authority does Hillel’s calendar have to determine these dates? From where do we learn that the Roshei Chodoshim and Yomim Tovim for thousands of years to come could be determined based on Hillel’s foresight, and that his predictions are halachically valid?
Basic Princples Granted Moshe
The Rambam (Hilchos Kiddush HaChodesh 5:2) held that Moshe Rabbeinu was entrusted with two different ways of inaugurating the new month. When the Sanhedrin was active, they would inaugurate the new month on the basis of the witnesses’s testimony. When the Sanhedrin would be disbanded, the lunar months would be determined based on a practical system, in which the lunar year and the solar year would maintain some degree of congruence. It was just such a system that Hillel based his calendar upon. The Rambam, ibid, end of chapter 5 and in Sefer HaMitzvos: Positive Commandment 153, writes that only the Beis Din of Eretz Yisroel has authority to determine Rosh Chodesh. Since Hillel was the Nassi of Eretz Yisroel, his decisions are binding (Meshech Chochma, Parshas Bo). Hillel’s calendar was based on a number of halachic principles including “molad zakein – do not consider a previous appearance of the moon.” According to this principle, if the moon appears in the afternoon, that day is not Rosh Chodesh, but rather the day after.
Were these principles given to Moshe Rabbeinu on Har Sinai, with the specific instruction that they be incorporated into the calendar when the Sanhedrin would be disbanded? Or perhaps Moshe Rabbeinu was given general instructions to develop a calendar that would reach the required results (that Pesach must be in the spring, and so on), and the specific details were left to Sages of future generations to develop as necessary?
Down To All The Details
The Brisker Rav held that even the specific details of how to develop the calendar were given to Moshe Rabbeinu on Har Sinai (Chiddushei Maran Riz HaLevi: Kiddush HaChodesh, Yoma, Sukka p. 8). The Chazon Ish, however, held that Moshe Rabbeinu was only given the general instruction to develop a working calendar, and the details were left to the Sages of future generations to decide (see Chazon Ish O.C. 140 s.k. 3). Hillel’s calendar was authorized by his Beis Din: Whereas the Rambam held that Moshe Rabbeinu was originally instructed in two ways of deciding Rosh Chodesh – by Beis Din or by (in inclement weather) calendar; the Ramban argues that Moshe was told only to inaugurate the new month by means of Beis Din. According to the Ramban, Hillel’s calendar represents the decision of his own Beis Din that it was binding for all future generations. They foresaw and sanctified all future months until the Sanhedrin would be reinstated (Ramban’s gloss on Sefer HaMitzvos, ibid. See also the opinion of the Rambam ibid:13; Sefer HaMitzvos: Positive Commandment 113). When necessary, Beis Din can set a date for a month to begin, long before that month arrives.
Rabbeinu Saadiah’s View
Interestingly, Rabbeinu Saadiah Gaon writes that even in the times of the Sanhedrin, they also made use of a calendar to predict when the moon would appear. The testimony of the witnesses was used only in adherence to the mitzvah that commands that witness testify.