[Avodah] 10 B'Teves on Shabbos

[Zev Sero]

Danny Schoemann wrote:
> In response to one of my Halocho-a-day posts kitzur.com/7zq2
> (http://halocho.blogspot.com/2009/01/halocho-244-fasting-on-shabbat-is.html)
> people keep on writing in informing me that if 10 B'Teves were to
> [theoretically] fall on Shabbos, we would fast.
> 
> Over the years I've heard this from various people.
> 
> Where does this Halocho come from?

The BY brings this in the name of the Avudraham, ultimately based on the
pasuk "be'etzem hayom hazeh".

Since it's only a hypothetical, I don't think it counts as a psak din,
and I speculate that if it were a practical question that needed a psak
then the halacha would be paskened otherwise.  It seems to me that if
this had been actually practised when there was kidush hachodesh al pi
hare'iyah, then there would have been some mention of it in the gemara.
The fact that the earliest mention of this idea is in the geonim tells
me that they were engaging in harmless speculation, not rigorous psak.
If kidush hachodesh is renewed before Moshiach comes then the BD that
does so can also pasken this question; and once Moshiach comes it will
become a yomtov anyway, so it will be just like any yomtov that falls
on Shabbos.


> The SA in OC 550:3 says "if these 4
> fasts fall on Shabbos that are deferred to Sunday."

That refers only to the three that can fall on Shabbos; since this one
can't, there's no need for the SA to address the case.

-- 
Zev Sero                    A mathemetician is a device for turning coffee
zev at sero.name               into theorems.                   - Paul Erdos