| Case | Ruling | Reason |
|---|---|---|
| May one work on Tisha B'Av? | Where the custom permits, yes; where it forbids, no | — |
| What of a talmid chacham? | Tanna Kamma: Everywhere, he refrains | — |
| Rabban Shimon ben Gamliel: One should always make himself a talmid chacham | — | |
| May one work on erev Pesach (until midday)? | Chachamim: In Yehuda, yes — until midday; in the Galil, not at all | — |
| And the night before? | Beis Shammai: Forbidden | — |
| Beis Hillel: Permitted until sunrise | — |
Tisha B'Av is a day of mourning, and a mourner is barred from melacha — so why does the mishnah leave working to local custom rather than forbidding it outright? Because an avel's ban on work binds only in fresh mourning; over a loss as ancient as the Churban it eases, and what remains is minhag, varying by place. The Meiri adds a grace note: the talmidei chachamim sit idle on Tisha B'Av, since they, more than anyone, feel the absence of the Place.
Why does Beis Hillel allow work on the night before, and forbid it only once the day itself begins? Hon Ashir answers by comparing the day to a fast. On Yom Tov, melacha is set aside so the day can be enjoyed — the restriction serves oneg. Erev Pesach is the reverse. Work is set aside not for the day's pleasure but for its labor: the hours are needed for clearing the chametz and baking the matzah, and, while the Mikdash stood, for making sure the Korban Pesach was not neglected. Because that need belongs to the daytime, the restriction belongs to the daytime too, and the night before stays open — just as a fast is kept by day and not the evening before. The mishnah's Tisha B'Av clause has the same shape: the night is permitted, the day is restricted, and in both the reason lives in the day itself.
Rabban Shimon ben Gamliel says: let a person make himself like a talmid chacham and refrain from work on Tisha B'Av — and no onlooker will suspect yuhara (showing off), since they assume he simply has no work. Yet in Berachos, on a chasan who would recite Shema on his wedding night, it is Rabban Shimon ben Gamliel who does worry about yuhara — and the Rabbanan who do not. The same Tanna, the opposite stance. How do the two stand together?
Alongside the fixed disciplines of the day, the series notes one that lives as custom: refraining from work. Its place-by-place variation, and the push for talmidei chachamim to keep it everywhere, show the Churban-mourning being woven into ordinary communal life rather than imposed by a single rule.