Because of two New Moons may the Sabbath be profaned: [the New Moon] of Nissan and [the New Moon] of Tishri, for on them messengers used to go forth to Syria, and by them the set feasts were determined. And while the Temple still stood the Sabbath might also be profaned because of any of the New Moons, to determine aright the time of the offerings.
m. Rosh Hashanah 1:4
The New Moon of Tishri is, of course, what the Rabbis referred to as Rosh Hashanah, the head of the year,
or what the biblical texts refer to as Yom T’ruah, the day of horn blasts (Num 29:7-11), and Zikron T’ruah, a remembrance by horn blasts (Lev 23:24-25). By fixing that day, it also enabled the date of the Festivals of Purgation and Booths to be determined. The New Moon of Nissan was significant because it determined when the Festival of Unleavened Bread and Passover occurred. Because the Sabbath injunction was to not do any work, there were various rules about what constituted work. One of these rules fixed the amount of journeying or walking one could do before they violated the Sabbath. Unfortunately, that distance was often less than had to be done for witnesses to communicate to the Sanhedrin in Jerusalem that they had seen the New Moon. However, because there was a biblical command to proclaim the holy convocations in their appointed seasons, Jewish sages and authorities who supported the extra Sabbath regulation believed they had a loophole which allowed those who enabled them to keep this commandment to travel as far as possible to do so:
For it is written, These are the set feasts of the Lord, even holy convocations which ye shall proclaim in their appointed season (Lev 23:4).
m. Rosh Hashanah 1:9
The Mishnaic Musings are a periodic series of posts where I reflect on one thing or another in the compendium of the Oral Law (the Mishnah) as I read through it for the first time. Quoted portions are taken from Hebert Danby’s eminent single-volume edition, The Mishnah, published by Oxford University Press.