Kiddush Hachodesh: The Mitzvah for Each Person

Each person who is able, has a mitzvah to be familiar with the workings of the Jewish Calendar (Shabbos, 75a). There are several points of view as to the extent of the obligation, including the following:

To Rashi and Maharsha, each person is required -- according to ability -- to study astronomy in connection with the calendar, but that the calculations required to determine the months are only the duty of the High Court. The Yerei'im taught that each person is required to be able to calculate the months, not only the Beis Din!

According to the Rambam, the Talmud required a basic knowledge of astronomy (see Magid Harakiah pp. 17-21).

Determining the Calendar: Review of Kiddush Hachodesh

We began our discussion regarding Kiddush Hachodesh last year (Outline Vol. 1, # 12):

In determining the Jewish lunar month, three elements must be taken into account: The "molad" (calculated conjunction), the actual conjunction and the visual sighting of the witnesses (corresponding to the moon's first phase).

The "molad" is the conjunction between the sun and the moon, when the moon is centered between the sun and the earth, and cannot be seen. However, the Torah says that... the moon... [must be] spotted by witnesses, and this only occurs hours later, at the beginning of the moon's first phase. This stage is referred to as "chiduso shel lavana" -- the renewal of the moon's cycle.

One of our readers asked whether it is the crescent moon which determines the months, or the molad.

The Calculation in Ancient Times

Today, the calculation determines the (average) molad, not the actual crescent.

However, there is a great dispute as to how the calendar was fixed in ancient times.

Previously, we cited Rebbenu Bachaye and the Rashba, who held that the determination was not based on the observation of witnesses, but was entirely based on the calculation.

However, Magid Harakiah concludes that the two authorities -- Rebbenu Bachaye and the Rashba -- have differing views. Although both agree that a calculation is the sole determining factor, they have slightly different calculations: Rebbenu Bachaye understood that the calculated molad determines the new month. According to the Rashba, however, additional hours must be added to insure that witnesses could possibly see the moon. In other words, although it was not necessary for witnesses to see the moon, the calculation must yield the time of the moon's first phase (the crescent), rather than the molad (conjunction).

The opinion of the Rashba fits in well with another discussion of ours.

Use of Telescopes in Kiddush Hachodesh (From Outline Vol. 1,12)

Moadim Uzmanim relates a contemporary debate: The visual sighting in ancient days was performed, of course, without aid of instruments. If the power of the court were resumed today, would the witnesses use telescopes to arrive at a closer determination of the conjunction?

1. The Chazon Ish would allow the telescope.

2. The Brisker Rav, however, would not: From Rashi's commentary to the Torah the six hours between the actual molad and the sighting of the witnesses is an eternal "shiur" (legally binding measurement).

The meaning of this obscure passage [from the Brisker Rav] would seem to be the following: The sanctification of the moon is not determined by the actual molad (conjunction), but by the appearance of the moon's first phase. Therefore, the fact that by use of telescope the molad can be detected earlier, has no affect on the determination of the month. It is still several hours before the first phase of the moon is detected here on earth...

The Brisker Rav's thinking coincides with the Rashba's: the determining factor should be the first phase of the moon, not the conjunction.

Rabbi Yaakov Bernstein
Kollel of Kiryas Radin
11 Kiryas Radin
Spring Valley, NY 10977
Phone: (914) 362-5156
E-mail: yaakovb@torah.org

Good Shabbos!

Text Copyright © '98 Rabbi Yaakov Bernstein and Project Genesis, Inc.