| Case | Ruling | Reason |
|---|---|---|
| Nissan | Messengers go out | Pesach |
| Av | Messengers go out | The fast |
| Elul | Messengers go out | Rosh Hashanah |
| Tishrei | Messengers go out | To set the festivals |
| Kislev | Messengers go out | Chanukah |
| Adar | Messengers go out | Purim |
| Iyar — when the Beis HaMikdash stood | Messengers go out | Pesach Katan |
Once the beis din sanctified the new month, the news still had to reach the whole nation. Messengers — shluchin — carried it out from Yerushalayim across Eretz Yisrael and beyond, but only for six of the twelve months: the journey was hard, and only months bearing a yom tov needed precise dating. An older method, beacon-fires lit mountain to mountain, had been sabotaged by the Kutim, who lit them at the wrong time; the messenger system replaced it (Rosh Hashanah 2:2). Word of the calendar moved at the speed of a walking man.
The list is curated. Sivan is absent though it holds Shavuos — because Shavuos is counted fifty days from Pesach, not dated from its own Rosh Chodesh (Tosafos Yom Tov). And among the fast-months only Av appears: after the Churban the other fasts — the Tenth of Teves, the Seventeenth of Tammuz — were left to each person’s choice, on the strength of Zechariah’s promise that the fasts would one day turn to joy (Rosh Hashanah 18b); only Tisha B’Av, its griefs doubled, stayed firmly kept — so only for Av did the messengers go (Rambam, Tosafos Yom Tov).
The perek’s treatment of dating the month opens with its last stage — sending the messengers — before the earlier stages, the sighting and the testimony, are even taught. Melechet Shlomo reads it as of a piece with the perek’s opening run of numbered lists: four new years, then six months, then two. Another way to hear it: the messengers must be named first so that the next mishnah — where witnesses may profane Shabbos because those messengers must reach as far as Suria — can land in context.
The messengers go out for Av ‘because of the fast.’ But was Tisha B’Av kept as a fast while the Second Bais HaMikdash still stood? Lechem Shamayim reads our mishnah as speaking only of the time after the Churban — and whether the Churban-fasts were observed at all during the Second Temple is itself disputed. (See Rambam’s Peirush and the Tashbetz.)
The series turns here from what the Churban took to how we live in its light. Where the mishnah just before it asked which mitzvos end with the Bayis and which endure, this one watches an enduring institution — the fixing and spreading of the calendar — quietly carry the Churban inside it: the messengers go out for Av ‘because of the fast,’ and the list marks off Iyar’s Pesach Katan as something only ‘when the Beis HaMikdash stood.’ The machinery of Jewish time still remembers the Mikdash.