Shulchan Aruch Orach Chaim 492 discusses the custom some have to fast on Monday, Thursday and Monday (BaHaB) following the months of Nissan and Tishrei. Rama in his gloss notes that the custom is to fast starting from the first available Monday of the following months (i.e. Iyar and Marcheshvan). (I assume he means to exclude where the first Monday of the month is Rosh Chodesh.)

Now, consider a case where Rosh Chodesh Iyar (say) is on Friday and Shabbat. I would have thought that BaHaB would start on the first Monday in Iyar (the third of the month).

However, Mishnah Berurah 492:3 implies that BaHaB actually starts the following Monday (the tenth of the month), writing that on the Shabbat following Rosh Chodesh (in our case the eigth of the month) we bless those who will fast BaHaB, and BaHaB then begins on the following Monday.

Why is this the rule? Is there a problem blessing those who will fast BaHaB on Shabbat Rosh Chodesh, such that the blessing, and thus BaHaB itself must be pushed off by a week? What would the problem be?


1 Answer 1


The לוח דבר בעיתו explains (regarding Rosh Chodesh Iyar 5769) that the reason we don't announce בה"ב on Rosh Chodesh is that:

אין מברכים את המתענים בה"ב בחדש ניסן או בשבת ר"ח, השבת הקרובה, כמו שנאמר (קהלת ז, יד) "בְּיוֹם טוֹבָה - הֱיֵה בְטוֹב", ומברכים בשבת שלאחריה.‏

I.e. In a time of good fortune, enjoy the good fortune (Koheles 7:14) - so we don't want to mention the fast (which is to atone for the sins caused by the good times) during those days which are happy - i.e. the month of Nissan and the demi-festival of Rosh Chodesh.

As in: Why dampen the atmosphere by mentioning an upcoming fast.

His source seems to be the MaHaril in his chapter on סדר שני וחמישי. (Hat tip: Joel K)

  • 1
    So then why ever do it on Shabbat? Do it on Sunday or Saturday night
    – Double AA
    Commented May 13, 2019 at 15:22
  • 1
    This seems to come from Maharil hebrewbooks.org/pdfpager.aspx?req=42570&st=&pgnum=49 (@DoubleAA)
    – Joel K
    Commented May 13, 2019 at 16:53
  • @DoubleAA - my guess: Because that's when "everybody" is in shul - so we announce/bless it so everybody will know about it. Commented May 14, 2019 at 7:47

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