Shulchan Aruch O.C. 553:2 states that eating on Erev Tisha B'av must end while it is still daylight.

In viewing the topic of tosefet Shabbat which is mentioned in Talmud Rosh Hashannah 9a, I understand why Shabbat and Yom Tov begin before nightfall.

The term used in the Talmud is מוסיפין מחול על קודש - "We add from the profane to the holy" or, in this case, we add time from the weekday to the holy Shabbat or Yom Tov.

Why would this apply to Tish'a B'av, though? What is the "holiness" in Tish'a B'Av? There is no prohibition of melacha as there is on Shabbat and Yom Tov.

Even more puzzling is that when Tish'a B'Av is observed on Sunday, as is this year, we still begin the fast before the end of Shabbat. That seems like we're doing the opposite by adding from the "profane" onto the "holy".


I think we may have a different reading of this. See be'er hetev #2 on the page you linked -- "one need not add any of the daytime to the fast"; the fast starts exactly at sunset.

When Tisha B'Av is a Saturday night, we stop eating at sunset because maybe the fast has already begun; but don't do work until the stars come out, as then we're certain Shabbos is over. (Play it safe both ways.)

(Now if someone was looking for an ultra-super-chumra of the week, they might want to follow R' Eliezer of Mintz, that halachic "sunset" is actually 18 minutes earlier than the sunset we observe. But I've never, ever seen anyone apply that to Tisha B'Av.)

  • Shalom - perhaps, I'm being to "picky" within mentioning the timing. I'm more interested in the tosefet aspect rather than the exact time. Why don't we start the fast at nightfall. I'm going to edit the question, so it lessens the confusion.
    – DanF
    Jul 22 '16 at 15:31
  • @DanF There is no evidence of Tosefet anywhere (at least that you've provided). You appear to be making up its existence and asking why it exists.
    – Double AA
    Jul 22 '16 at 15:35
  • 1
    @DanF we do start the fast at nightfall! The Mechaber reads: "only eat while it is still day; twilight is prohibited." You can continue eating until the very last split-second of sunset. No tosefet. Or is your question about those who officially declare they're starting the fast early?
    – Shalom
    Jul 22 '16 at 17:52
  • We stop eating and drinking at sunset, the time the "hafsaka" begins. And at the same time we no longer wash, anoint or have sexual relationships. However when this is on Shabbat, we do not stop wearing leather shoes at this point but continue wearing them until nightfall.
    – CashCow
    Jul 25 '16 at 9:07

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