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Shabbat Parashat Tzav | 5770

Hemdat HaDaf HaYomi: Until when can you recite Kiddush Levanah? (41b-42a)

Rav Ofer Livnat

Nissan 6-12, Sanhedrin 37-43

This week in the Daf Hayomi, the Gemara (41b) deals with the question of when the latest time to make the blessing on the new moon is. Since the moon disappears and reappears at the beginning of each month, the Sages instituted a blessing on the new moon. The Gemara quotes a disagreement as to when the moon is still considered new, and the blessing can still be said. One opinion is that one can wait until seven days, and the other opinion is until sixteen days. The Gemara explains that the opinion that holds seven days claims that the blessing can be made until the moon is half full. The opinion which states until sixteen claims that the blessing can be made until there is a full moon. The Halacha follows this opinion.

The Rishonim found difficulty with the opinion that the blessing can be made until sixteen days, since if it means until the sixteenth day of the month, then that would be after the moon has become full and is actually beginning to decrease. The Yad Rammah explains that, even though it has begun to decrease, since it still appears to be full, the blessing can be made. However, as a result of this problem, some Rishonim suggested other explanations to the Gemara.

One suggestion was that sixteen was not inclusive, and the blessing can be made only until the fifteenth day. This was the explanation of the Or Zaruah (Hilchot Rosh Chodesh 456) and the Tur (Orach Chaim 426). The second suggestion was that sixteen is not referring to days of the month, but rather to days from the molad (the new moon, when the moon is exactly in between the earth and the sun).

If these two suggestions are combined, we receive fifteen days from the molad, which is indeed the way the Tur (ibid) rules. This time is significantly earlier than the sixteenth of the month, and is much closer to the middle point of the month.

However, the Maharil (19) did not find this calculation to be sufficient. He claims that when the Gemara stated sixteen it did not really mean sixteen, and a more exact calculation must be made of the middle point of the month. The length of the lunar cycle changes from month to month, and for purposes of setting the calendar, an average length of a month is used. The average length used is 29 days 12 hours and 793 chalakim (in each hour there are 1080 chalakim). The Maharil states that one should take half of this time, add it to the molad, and this is the end point for saying the blessing on the new moon. And even though this calculation is not exact as well, since it is based on an average calculation, it is closer to the exact middle point of the month.


Summary and Ruling:

The Mechaber (Shulchan Aruch Orach Chaim 426, 3) rules like the opinion of the Tur that the blessing can be said until fifteen days from the molad. The Remmah (ibid) rules like the Maharil that the blessing can be said until half of 29 days 12 hours and 793 chalakim from the molad. The Be'ur Halacha (ibid) writes that if one did not say the blessing before this time, he can rely on the opinion of the Mechaber and say the blessing until fifteen days from the molad. After this point, one can say the blessing without saying Hashem's name until the sixteenth of the month, like the Rishonim who understood the Gemara based on its simple meaning.      


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This week’s Hemdat Yamim is dedicated in loving memory of
R' Meir ben
Yechezkel Shraga Brachfeld

Hemdat Yamim is endowed by
Les & Ethel Sutker of Chicago, Illinois in loving memory of
Max and Mary Sutker and
Louis and Lillian Klein, z”l.


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