When Asarah BaTeves falls on Shabbos
בן-אדם כתב-לך את-שם היום את-עצם היום הזה סמך מלך-בבל אל-ירושלם בעצם היום הזה
Son of Man, write for yourself the name of today. On this very day, the King of Babylonia began his siege on Jerusalem, on this very day
Of the four minor fasts in commemoration of the destruction of Jerusalem and the Temple, the tenth of Teves is unique. This fast, which is in commemoration of the beginning of the siege on Jerusalem, is the only fast in our present calendar that can fall on a Friday. It creates an unusual situation where we go into Shabbos having not eaten the entire day prior. Usually, a person shouldn’t go into Shabbos hungry. This day is the exception. While this in fact happens this year, 5781, it’s also a very infrequent occurrence. Although it will happen again in two years, it’s been 20 years since it last happened. Something else that’s unique about the fast known as Asarah BaTeves is that in our present calendar, it cannot fall on Shabbos. The other fast days can. However, since it is forbidden to fast on Shabbos (besides Yom Kippur), they get pushed off until Sunday. This situation doesn’t occur for Asarah BaTeves, as it cannot fall on Shabbos anyways.
Nevertheless, the Abudraham records an interesting halacha. He says that if Asarah BaTeves were to fall on Shabbos, it wouldn’t get pushed off to Sunday. Since the verse alluding to this fast says the phrase בעצם היום הזה, on this very day, just like it says by Yom Kippur, it cannot be any other day. This is understood to mean that in this hypothetical situation, we would fast even on Shabbos. Even though this is normally forbidden, for some reason Asarah BaTeves is different. How could this be? How could the obligation to fast override the obligation to delight and have physical pleasure on Shabbos?
One could ask on the other fast days: why does Shabbos push them aside? Delighting on Shabbos and not fasting is a mitzvah from the Prophets, just like the Four Fasts is a mitzvah from the Prophets. These two mitzvos of equal stature should cancel each other out, with the result being to passively do nothing. As such, fasting should override Shabbos. One suggestion could be that the fasts were never enacted to be on a certain day. As we see, the Prophet describes the Four Fasts as “the fast of the fourth [month], the fast of the fifth [month], the fast of the seventh [month], and the fast of the tenth [month]”. It was the Rabbis who enacted specific days in those months. That would mean then that these fasts couldn’t override Shabbos, whose mitzvah to eat is purely from the Prophets.
This could answer the question regarding Asarah BaTeves. Unlike the other fasts, it says בעצם היום הזה, on this very day. This means that the Prophet had in mind specifically to fast on the tenth of Teves. That would make it impossible to push to after Shabbos. If Asarah BaTeves would fall on Shabbos, then we would have to fast on Shabbos. It’s just as stringent as the mitzvah to eat on Shabbos, making the two cancel out. Therefore, passively doing nothing would be the proper thing. However, one could simply explain the reason that Shabbos pushes the fasts aside is because the Prophets made this part of their enactment. They knew their fast days would fall on Shabbos, and decreed they should be observed the next day.
Another approach to explain how Asarah BaTeves could override Shabbos is to connect it to the concept of a Ta’anis Chalom. Chazal said that someone who had a bad dream which is very worrisome and highly nerve-wracking should fast. Fasting will annul any potential decree of calamity that the person is concerned for. What’s surprising is the halacha is that if the bad dream occurred on Shabbos, the person would fast even on Shabbos. This is because the fast should be on the exact day that the dream occurred. We see then a precedent that a fast which must occur on a certain day can be done even on Shabbos. The same would then be true for Asarah BaTeves, since the fast has to be on the very day the siege began.
The problem with this approach is that the two fasts are not comparable. The reason that fasting a Ta’anis Chalom is permissible on Shabbos is because it is a fulfillment of delighting on Shabbos. Someone who had a very worrisome dream will be a nervous wreck all of Shabbos. They won’t be able to enjoy the food that they are eating. They will be anxious and uncomfortable. If they fast, knowing that it will serve as an atonement and rectify the dream, that will give them the greatest pleasure. It will be to them as if they ate a delicious banquet. None of this is relevant for Asarah BaTeves.
Due to the difficulties involved with this innovative law, Rav Asher Weiss wants to suggest an entirely new approach. When Abudraham says that if Asarah BaTeves would coincide with Shabbos, it couldn’t be pushed to after Shabbos, his intent isn’t to fast on Shabbos. Rather, since Asarah BaTeves has to occur on the day itself, and it’s forbidden to fast on Shabbos, the result is that Asarah BaTeves wouldn’t be observed that year. The following year there will be Asarah BaTeves, but not that year. All the authorities from the past centuries assumed there was this big innovation with Asarah BaTeves, but in reality just like the other fast days, this one wouldn’t override Shabbos. Still, is there any way to resolve the understanding that one would fast on Shabbos if it would coincide with Asarah BaTeves? Perhaps an understanding of the essence of Asarah BaTeves would help.
One could ask why it’s even a fast day. Nothing significant seemingly happened on that day. Sure, the Babylonian King began his siege on Jerusalem. But there wasn’t any physical damage. Nothing was destroyed. No walls were breached. Why is it designated as a fast? Especially compared to Tisha B’Av, which was the actual destruction. If that day doesn’t push aside Shabbos, why would Asarah BaTeves? Furthermore, Jerusalem was under siege many times throughout history. What was significant about this siege?
What made this siege different was its significance to the eventual destruction. The day that the siege took place was the day that the Heavenly Court decreed the destruction of Jerusalem. We are taught that every year that the Temple isn’t rebuilt, it’s as if it was destroyed anew. That means that each year on Asarah BaTeves, there’s another court case in Heaven. If the Temple won’t be rebuilt that year, that decree will be made on Asarah BaTeves.
Most fasts are in commemoration of some past tragedy. Some people fast on the yartzheit’s of their parents. Tisha B’Av commemorates the destruction of Jerusalem. These types of fasts don’t override Shabbos. However, as we mentioned, a Ta’anis Chalom is permitted, as fasting that day would give the person pleasure. By fasting, their hope and prayer is they will annul any future calamity that may come upon them. The prospect of that occurring gives great pleasure. The same is true with Asarah BaTeves. We fast as a hope and prayer that this Asarah BaTeves will create a ruling in Heaven that the Temple will be rebuilt. We hope that there won’t be another destruction. This gives the greatest pleasure. It’s no wonder then that the fast could occur even on Shabbos.
Good Shabbos, and have an easy fast.
 Based on Minchas Asher Moadim Daled Tzomos § 43, a shiur he gave in Teves 5781 to Agudas Yisroel’s Virtual Yarchei Kallah, and Chasam Sofer’s Toras Moshe I Derush L’Zayin Adar s.v. כתו’ בה”ג, printed after parshas Vayikra and parshas Shekalim
 Ezekiel 24:2
 Mishneh Torah Hilchos Ta’aniyos 5:2
 Ba’er Heitev to Shulchan Aruch Orach Chaim 550:3 § 4 and Mishnah Berurah ad. loc. § 10. See Magen Avraham ad. loc. § 5
 Bach to Tur Orach Chaim § 249, brought by Magen Avraham ad. loc. § 7
 Shulchan Aruch Orach Chaim 550:3
 Abudraham Hilchos Ta’anis p. 254, brought by Beis Yosef to Tur Orach Chaim § 550 s.v. וה”ר דוד. The latter doesn’t reject this law, but simply questions its source. However, Rav Asher Weiss notes that this ruling goes against many Rishonim. For example, Rashi to Megillah 5a § אבל זמן and Rambam in Mishneh Torah loc. cit. § 5. The Ibn Ezra also clearly rejects this, since in his Shabbos Zemer כי אשמרה שבת which he composed he writes: על כן להתענות בו על פי נבוניו אסור לבד מיום כפור עוני. Although, Rav Asher Weiss admits that this could just be according to our calendar, where this Abudraham is only hypothetical. Regarding Rashi, see Shoel UMeishiv 1:3:179 and Rav Asher Weiss’ rebuttal. Regarding the source for the Abudraham, see Ohr Sameach ad. loc. § 6 who suggests a source. Although, Rav Asher Weiss shows its not foolproof. See also Aruch HaShulchan Orach Chaim 549:2, who says we don’t rule like this Abudraham
 Ezekiel loc. cit.
 Leviticus 23:29. Rav Asher Weiss questions the connection of the verse in Ezekiel to this one. That one is dealing with when the siege was. The verse of Yom Kippur is detailing which day to fast on. We don’t see from there that the fast of Asarah BaTeves must be on that very day
 Minchas Chinuch § 301
 וקראת לשבת עונג (Isaiah 58:13)
 See Kiryas Sefer to Mishneh Torah Hilchos Shabbos Chapter 29, who says that fasting the entire Shabbos is a biblical prohibition. Only partially fasting on Shabbos is from the Prophets. However, Rav Asher Weiss fails to figure out what the prohibition would be. Either way, see Ohr Sameach loc. cit. who applies this to the Four Fasts, which are only from sunrise to nightfall, and not the entire Shabbos.
 Zachariah 8:19
 See Tashbetz 2:271 and Ritva to Ta’anis 26b and Rosh Hashanah 18b who seem to say similarly, although it’s not definitive
 Cf. note 9
 Rav Asher Weiss feels this explanation is so obvious, he’s at a loss to explain why the Minchas Chinuch doesn’t suggest it. He explained that perhaps the Minchas Chinuch felt that since a fast day that is pushed aside is more lenient, the Prophets wouldn’t have made it part of their initial enactment. See Rav Asher Weiss’ other questions on the Minchas Chinuch
 Rav Chaim Soloveitchik in Chiddushei HaGrach Al HaShas Rosh HaShanah § 44. This work was compiled by his students. For some reason it’s written that the innovation regarding Asarah BaTeves was said by the Bahag. This seems to be a typo
 Shabbos 11a; Ta’anis 12b
 Ibid; Mishneh Torah Hilchos Ta’aniyos 1:12; Shulchan Aruch Orach Chaim 288:4
 Rav Asher Weiss doesn’t give Chiddushei HaGrach Al HaShas as much credence as Rav Chaim’s sefer on the Rambam, which Rav Chaim himself wrote. Therefore, Rav Chaim didn’t try to defend this question on this explanation
 Tur Orach Chaim § 288; Darkei Moshe to § 529; Magen Avraham to Shulchan Aruch Orach Chaim 597:1 § 1
 Rav Asher Weiss admits that he has no problem arguing on everyone since this is only hypothetical. If this were a practical question, he would nullify his opinion to those who came before him and say to fast the day after Shabbos
 From here to the end is the Chasam Sofer loc. cit.
 Many sources quote the expression כל דור שלא נבנה בית המקדש בימיו, כאילו נחרב בימיו, including the Chasam Sofer. The Chofetz Chaim in Shemiras HaLashon II Chapter 7 quotes it from Chazal. However, we don’t seem to have this exact phrase from Chazal. Something similar appears in Yerushalmi Yoma 1:1 and Midrash Tehillim 137:1: כל דור שאינו נבנה בימיו מעלין עליו כאילו [הוא] החריבו. This version sounds harsher, as it says that it’s as if the individual destroyed it. The one the Chasam Sofer quotes is more indirect, saying that it’s “as if it was destroyed”. The earliest source for this softer version that I found was Sheivet Mussar Chapter 50, published in 1731
 See Derashos Chasam Sofer I p. 99 col. 4 s.v. ועד”ז, who proves from this week’s parsha that mourning for the Temple actually does override having delight on Shabbos. Before Yosef revealed himself to his brothers, he slaughtered animals for a big feast. It’s taught in Bamidbar Rabbah 14:2 that this was on Erev Shabbos, and he prepared the meal for Shabbos. The next day, on Shabbos, is when Yosef revealed himself to his brothers. The verse says that Yosef fell on Binyamin’s neck and cried (Genesis 45:14). It’s taught in Genesis Rabbah 93:12 that he was mourning the future destruction of the Temple, which was to be built in the portion of Binyamin. We see it’s permissible to mourn the Temple, even though normally crying would be an infringement of delighting on Shabbos. The Chasam Sofer says we see from here that mourning the Temple overrides Shabbos, and it’s no wonder then why it’s permissible to fast on Asarah BaTeves on Shabbos. He clarifies though that this is only true for Asarah BaTeves, as it was the beginning of the tragedy. See there