הלל נשיאה

Hillel Nesia (Hillel the Second), Nasi of the Sanhedrin in Eretz Yisrael in the fourth century, stood in the fifth generation of the Amoraim of the Land — the generation of Abaye and Rava in Bavel — and the sage under whose hand the fixed Jewish calendar was established. A descendant of the house of the Nesi’im, the dynasty of Hillel HaZaken that passed through Rabban Gamliel and Rabbi Yehudah HaNasi, he is cited in the writings of the Geonim and Rishonim as Hillel the son of Rabbi Yehudah Nesiah. In two places his name is joined to matters of halachah: in one, Rabbi Yose ben Avin expounds a law before him; in the other, Hillel himself cites a mishnah to establish the din.

His Nesiut fell in bitter times. With the empire’s turn to Christianity came persecutions; many yeshivot of Eretz Yisrael were destroyed, and in the suppression of the revolt of the days of Gallus, Tzippori and other cities were laid waste, while the emperor Constantius forbade the very gatherings on which the Sanhedrin’s work depended. Relief came in the days of the emperor Julian, who showed the Nasi honor: he wrote him a personal letter assuring him of his friendship, informed the Jewish communities that he had burned the tax rolls, and before setting out for his Persian war directed “his brother, the venerable patriarch” to abolish the send-tax.

Until his day the beit din sanctified each Rosh Chodesh upon witnesses who had seen the new moon and weighed each leap year on its own, and all the golah depended on messengers carrying word of the Sanhedrin’s decisions — messengers now in danger, so that Rav Huna bar Avin once sent word to Rava in Bavel not to wait for the official ibbur. Seeing that the persecutions did not relent, Hillel rose with his beit din and established the calendar upon calculation for all time to come: Rosh Chodesh according to the molad and the mean course of the moon, and the leap years by a fixed reckoning. The mesorah, brought by Rav Hai Gaon and cited by Rav Avraham bar Chiya in his Sefer HaIbbur, sets this takanah in the year 4119/359.

The Ramban writes of him: from the year 670 of the count of shtarot, from the days of Hillel the son of Rabbi Yehudah HaNasi, the Sanhedrin ceased in Eretz Yisrael — “and it is he who established the seder ha’ibbur, reckoned the years, and sanctified the months for all the generations.” The Rishonim discussed whence his authority: some say a halachah leMoshe miSinai provides for a calendar set by calculation; others, that as Nasi at the head of a beit din of semuchim he sanctified in advance every month and year to come. The calendar he established is the one by which Klal Yisrael fixes the moadim to this day.