Starting with the Mishna in Ta'anis 1.4 we learn that there are occasions (lack of rain in this case) when we fast BeHaB, i.e. Monday, Thursday, and Monday.

הִגִּיעַ שִׁבְעָה עָשָׂר בְּמַרְחֶשְׁוָן וְלֹא יָרְדוּ גְשָׁמִים, הִתְחִילוּ הַיְחִידִים מִתְעַנִּין שָׁלשׁ תַּעֲנִיּוֹת. אוֹכְלִין וְשׁוֹתִין מִשֶּׁחֲשֵׁכָה, וּמֻתָּרִין בִּמְלָאכָה וּבִרְחִיצָה וּבְסִיכָה וּבִנְעִילַת הַסַּנְדָּל וּבְתַשְׁמִישׁ הַמִּטָּה:‏

If the seventeenth of Marheshvan came and no rain fell, individuals begin to fast three fasts. They eat and drink after it gets dark and they are permitted to do work, to bathe, to anoint themselves with oil, to wear shoes, and to have marital relations.

The reason given for Monday & Thursday being auspicious days for prayer is that Moshe went up to Har Sinai (the 3rd time) on a Thursday and came back after 40 days on a Monday.

But why Monday, Thursday, and Monday - why isn't it sufficient for the fasts to simply be Monday and Thursday?

Same question for our post-Yom Tov BeHaB - why do we need to fast twice on a Monday?

Searching for ideas and sources.


2 Answers 2


במסכת סופרים (פרק כא) מובא מנהג ארצישראלי להתענות שני וחמישי ושני זכר לשלושת ימי הצום שצמו מרדכי ואסתר המלכה בשושן הבירה, קודם שנכנסה אסתר למלך אחשוורוש, צום שחל באמצע חודש ניסן

This is from the hebrew wiki page about Baha"b. It says we fast thrice just like Mordechai and Esther did in the Meggila

  • 1
    This is saying that there was a custom to fast a tripartite Taanit Esther to commemorate how she fasted three days. It doesn't indicate that in general Bahab fasts are three days for that reason
    – Double AA
    Commented Oct 29, 2019 at 11:17
  • True, but one more piece of the puzzle; another "3 day" fast. Commented Oct 29, 2019 at 11:38

A possible answer I have posited to various people - I'm wondering what feedback I'll get from MiYodea.

As stated, Mondays and Thursday are special because Moshe went up to Har Sinai (the 3rd time) on a Thursday and came back after 40 days on a Monday.

So the order should be Thursday & Monday.

However, we cannot begin on Thursday, as we learned in Ta'anis 4:9, "so as not to cause panic which would cause prices to rise".

אֵין גּוֹזְרִין תַּעֲנִית עַל הַצִּבּוּר בַּתְּחִלָּה בַּחֲמִישִׁי, שֶׁלֹּא לְהַפְקִיעַ הַשְּׁעָרִים

Instead, we start on a Monday - which is one of the auspicious days. Since we want the Thursday-Monday cycle, we land up fasting Monday (as a runner up), then Thursday & Monday.

  • 1
    Then why doesn't the second round of fasts, which can start on a Thursday, only last two times?
    – Double AA
    Commented Oct 28, 2019 at 21:24
  • @DoubleAA - IDK - an idea: once we fast in sets of 3 then we always fast in sets of 3 - kind of Lo Plug. Possibly that's why R' Yossi argues to start the 2nd round on a Monday. (And that would be an answer: explaining why it's always sets of 3; but I couldn't locate a single explanation for that, unless you want to get to chazoko.) Commented Oct 29, 2019 at 9:43

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