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Start Of The Yeshiva Semester
‘Today Is Propitious…’
(Sanhedrin 65b – 66a)



Our sugya discusses the prohibition of lo t’onenu – refraining from guessing or fixing times for fortunate or unfortunate events. According to Rabbi Akiva, Vayikra 19:26 forbids us from refraining from doing something because we think the time is “unlucky” or, conversely, doing something because we think the time is “lucky.”


Astrology In Halacha

In the Rambam’s opinion (Hilchos Avodas Kochavim 11:9), Rabbi Akiva referred to astrologers as “liars, in whom fools believe.” Other rishonim agree with the Rambam that astrology is nonsense (Responsa Zichron Yehudah 91 by the son of the Rosh, 91, who cites Yad Ramah on our sugya and Rabbeinu Yonah in Shaarei Teshuvah, 3:86). However, many rishonim disagree (Ramban in the responsa attributed to him, 283; Tosfaos, Shabbos 156b, s.v. “Kaldai”; and Nimukei Yosef on our sugya). They believe there is truth in astrology and that astrologers should be heeded.

Why We Shouldn’t Explore The Future

In their opinion, the Torah’s prohibition concerns someone who makes up his own auspicious or inauspicious times. If a person, however, heard from an astrologer that he should refrain from some act on a certain day, he should heed his advice. Nevertheless, astrologers’ advice should not be sought, as the Torah says: “You should be straightforward with Hashem” (Devarim 18:13). In other words, we should trust Hashem and pray to Him that He should grace us with blessings and refrain from exploring the future and things concealed from us.

Rashi comments: “Go with Him in simplicity and hope to Him and do not explore the future but accept everything that comes upon you with simplicity, and then you will be with Him and His portion.” The Rema (Shulchan Aruch, Yoreh Deah 179:2) concludes that “what a person knows something to be specifically against the mazal, he should not act and rely on a miracle. Nonetheless, one must not seek out these matters because the Torah commands us to be straightforward.”


Omens On Hoshana Rabbah Night

In his commentary on the Torah (Bamidbar 14:9), the Ramban mentions that it is known that “on the night of [Hoshana Rabbah] the head of a person who will die in the ensuing year will cast no shadow.” The Abudarham (Seder Tefilas Sukkos, s.v. veyesh anashim)

writes that some people would wear a sheet on Hoshana Rabbah night and go somewhere exposed to the moon. They would then remove the sheet and spread their limbs to the moon. “If all their limbs are whole, it’s a good sign, but if his head’s shadow is missing, he should fear for his soul. If the shadow of one of his fingers is missing, it is a sign that one of his relatives is endangered: on the right hand – his sons; on the left hand – his daughters” (see Horayos 12a and Maharsha, ibid.).

Nonetheless, Rishonim assert that one should not do so as a person could thereby worsen his mazal, as not everyone is adept at examining his shadow and may become unduly afraid, as well as violate the commandment to be simple and straightforward (see Shach, Yoreh Deah 179:2).

Rishonim also write that performing a certain act at a certain time as a sign for mazal or a blessing is allowed. The Shulchan Aruch (Yoreh Deah 179:2) thus asserts that “people…have a custom to marry only when the moon is waxing or full” and the Semak (cited by the Rema, ibid.) writes that yeshivas start their semesters on rosh chodesh as a good sign. Indeed, yeshivas today also have the custom to end their vacations on the roshei chodashim of Elul, Cheshvan, and Iyar.