Showering During the Nine Days?!
The Mishnah in Maseches Ta’anis (26b) famously teaches that “Mishenichnas Av Mema’atin Besimchah”, ‘When the month of Av arrives (Rosh Chodesh Av), we lessen our joy’. Since many catastrophes and national tragedies befell our people during this time period, including the destruction of both of the Batei HaMikdash on Tisha B’Av, halachah dictates various restrictions on us in order to mourn our great losses, and properly commemorate by feeling the devastation. One of these restrictions is not to bathe during the “Nine Days”, the nine day mourning period from Rosh Chodesh Av until Tisha B’Av. Although bathing is noticeably absent from the Gemara’s restrictions of the Nine Days, all the same, this opinion of the Ravyah’s (an early Rishon) is codified as halachah by the Tur, Shulchan Aruch, and Rema (Orach Chaim 551: 16).
Nevertheless, and quite interestingly, the most common question a Rabbi is likely to receive this time of year is if it is permissible to take a shower during the Nine Days.
Although at first glance from a preliminary reading of Rabbinic literature on the topic, showering seems to be black-on-white prohibited, yet, from the works of many contemporary authorities it seems a better question would be if there is a hetter not to take at least some sort of shower during the Nine Days!
First of all, it must be noted that with the vast majority of world Jewry living in the Northern Hemisphere, the Nine Days (not so conveniently) falls out during the hottest part of year, during the blazing summer. When someone is asking his rabbi for a halachic dispensation to take a shower, he is not merely asking a theoretical question. It is usually someone sweating heavily, caked in perspiration and often afflicted from odoriferous emanations. This is especially germane this summer, with the mercury in Yerushalayim already hovering over 100°F (38°C) in June!
Hygiene or Pleasure?
If we were to ask our suffering friend why he wanted to take a shower, he would most likely reply “to get rid of the sweat and stickiness and feel like a human being again”. The Aruch Hashulchan, already in the 1890s, ruled that one whose body is dirty can bathe during the Nine Days (even using hot water) in order to get clean, since he is not bathing for pleasure. In other words, the Aruch Hashulchan is teaching us that the restrictions of the Nine Days are meant to lessen our enjoyment, not to force us to give up basic hygiene.
But, before we can question how the Aruch Hashulchan made such a distinction, it should be stressed that the halachos of the Nine Days parallel those of a mourner, and even a person mourning the loss of his parents is permitted to be ‘ma’avir es hazuhama’, ‘remove the sweat’, even during shiva, since it is not done for pleasure. The Mishnah Berurah adds that it’s so obvious that this is permitted during the Nine Days that there was no need for the Shulchan Aruch to even make mention of it.
Indeed, the Rambam and Ramban rule that the ‘Nine Days’ prohibition refers exclusively to pleasure bathing in hot water in an actual bathhouse. The Yeshuos Yaakov writes similarly that since the Nine Days constitute a mourning period akin to Sheloshim, and during Sheloshim a mourner may wash himself with cold water, so too during the Nine Days the only washing restriction should be pleasure bathing in hot water. On the other hand, it should be noted that not everyone concurs with this position, as the Rema (O.C. 551: 16) seemingly did not hold this way, but rather, following the precedent of the Terumas Hadeshen (vol. 1: 151), ruled that one may not wash his whole body even in cold water during the Nine Days.
An interesting proof several contemporary authorities cite is from Hilchos Yom Kippur. On Yom Kippur, the holiest day of the year, and the only biblically mandated fast day that comes with its own set of restrictions including washing, the Shulchan Aruch emphatically declares that only pleasure washing is technically forbidden. Although the Mishnah Berurah stresses that on Yom Kippur one should not rely on this unless in dire need, nevertheless, if hygienic washing to remove sweat on Yom Kippur is me’ikar hadin permitted, then it certainly should be permitted during the less stringent, rabbinically ordained Nine Days.
Another noteworthy factor is that several important Acharonim, including the Chayei Adam, Ben Ish Chai, Kitzur Shulchan Aruch, and Mishnah Berurahexplicitly permit certain types of washing on Erev Shabbos Chazon (head, arms, and legs) with hot water if one is accustomed to bathe every week. Several contemporary authorities, including Rav Moshe Feinstein zt”l and Rav Yosef Eliyahu Henkin zt”l, maintain that nowadays, with everyone (hopefully) showering more than once a week, this dispensation should include everyone taking a full hot shower, especially when deemed necessary. However, it should be noted that not all contemporary poskim agree with this chiddush lema’aseh. 
An interesting point raised by Rav Shlomo Zalman Braun zt”l, in his Sha’arim Metzuyanim B’Halachah, is that when Chazal enacted the original prohibitions of the Nine Days, the only way to bathe was to go for an enjoyable lengthy dip in a steamy bathhouse. But nowadays, with the advent of quick and easy showers, which are meant for a hygienic wash and not for pleasure bathing, it is possible that they would not be included in the prohibition. Remember, not too long ago showers were not very prevalent.
This ‘Shower Exclusion’ during the Nine Days for hygienic purposes is ruled decisively by the vast majority of contemporary authorities including Rav Yosef Chaim Zonnenfeld zt”l, Rav Yechiel Michel Tukachinsky zt”l, Rav Moshe Feinstein zt”l, Rav Shlomo Zalman Auerbach zt”l, Rav Yaakov Kamenetsky zt”l, the Klausenberger Rebbe zt”l, Rav Yosef Shalom Elyashiv zt”l, Rav Shmuel Halevi Wosner zt”l, Rav Ben Tzion Abba Shaul zt”l, Rav Ovadiah Yosef zt”l, Rav Mordechai Eliyahu zt”l, Rav Yisrael Halevi Belsky zt”l, Rav Efraim Greenblatt zt”l, the Sha’arim Metzuyanim B’Halachah, and Rav Moshe Sternbuch.
Conversely, and although there are differing reports of his true opinion, it must be noted that the Chazon Ish zt”l, the Steipler Gaon zt”l, as well as Rav Binyamin Zilber zt”l and Rav Chaim Kanievsky, are quoted as being very stringent with any showering during the Nine Days, even for hygienic reasons, and even while acknowledging that most other Rabbanim were mattir in specific circumstances.
Additionally, and quite importantly, this ‘Shower Exclusion’ is by no means a blanket hetter. There are several stipulations many of these poskim cite, meant to ensure that the shower will be strictly for cleanliness, minimizing enjoyment and mitigating turning it into ‘pleasure bathing’:
- There has to be a real need: i.e. to remove excessive sweat, perspiration, grime, or dirt. (In other words, ‘to actually get clean!’).
- One should take a quick shower in water as cold as one can tolerate (preferably cold and not even lukewarm).
- It is preferable to wash one limb at a time and not the whole body at once. (This is where an extendable shower head comes in handy). If only one area is dirty, one should only wash that area of the body.
- One shouldn’t use soap or shampoo unless necessary, meaning if a quick rinse in water will do the job, there’s no reason to go for overkill. Obviously, if one needs soap or shampoo to get clean he may use it.
Rav Shlomo Zalman Auerbach zt”l, while wryly noting that actual mourners do not usually ask for special halachic allowances related to the halachos of mourning as opposed to many who do so during the Nine Days, nonetheless cautions the overzealous among us not to forget about the spirit of the law. It is important for us all to remember that these restrictions were instituted by Chazal to publicly show our mourning during the most devastating period on the timeline of the Jewish year. Our goal should be to utilize these restrictions as a catalyst for inspiration towards Teshuvah. It is worthwhile to do so as well. As the Kaf Hachaim citing the Midrash relates, everyone who observes the halachos of the first ten days of Av, thereby demonstrating their personal mourning over the destruction of Yerushalayim, will merit witnessing ten incredible miracles reserved for the days of Moshiach. May it be speedily in our days.
This article was written lezechus Shira Yaffa bas Rochel Miriam and her children l’yeshuah sheleimah teikif u’miyad!!
Rabbi Yehuda Spitz serves as the Sho’el U' Meishiv and Rosh Chabura of the Ohr Lagolah Halachah Kollel at Yeshivas Ohr Somayach in Yerushalayim.
For any questions, comments or for the full Mareh Mekomos / sources, please email the author: firstname.lastname@example.org.
 See Mishnah in Maseches Ta’anis 26b and accompanying Gemara.
 See Gemara Yevamos 43a, Tosafos (ad loc. s.v. milisa, citing the Yerushalmi Ta’anis), and Tur, Shulchan Aruch, Rema and their commentaries to Orach Chaim 551.
 This is following general Ashkenazic minhag; many Sefardim only observe restrictions beginning the week that Tisha B’Av falls out on. Although there are several Sefardic authorities who maintain that Sefardim should follow the Ashkenazic minhag and start the restrictions from Rosh Chodesh Av [Including the Knesses HaGedolah (Orach Chaim 551: Haghos on the Tur 5), the Ben Ish Chai (Year 1, Parshas Devarim 4, 5, & 12), and Kaf Hachaim (Orach Chaim 551: 44, 80, & 142); although they generally only start immediately following Rosh Chodesh Av, as opposed to most Ashkenazic authorities who include Rosh Chodesh Av itself in the restrictions], nevertheless, most Sefardim are only noheg these restrictions from the actual week of Tisha B’Av as per the ruling of the Shulchan Aruch (Orach Chaim 551, 10). See Shu”t Yabea Omer (vol. 6, Orach Chaim 46 and vol. 9, Orach Chaim 50, 1), Shu”t Yechaveh Daas (vol. 1: 41 and vol. 4: 36), Rav Mordechai Eliyahu’s Darchei Halachah glosses to the Kitzur Shulchan Aruch (122: 19), and Yalkut Yosef (Kitzur Shulchan Aruch, Orach Chaim 551; 1). Many of these restrictions are generally still in effect until midday (Chatzos) of the next day, the tenth of Av (see Shulchan Aruch, Rema, and main commentaries to Orach Chaim 558),with some being makpid the whole next day for some of the restrictions (except in a year when Tisha B’Av is actually being observed on the tenth of Av, since it fell out on Shabbos).
 Although bathing is noticeably absent from the Gemara’s restrictions of the Nine Days, nevertheless, this opinion of the Ravyah (Avi Ezri vol. 3: 882) is codified as halachah by the Tur, Shulchan Aruch, and Rema (Orach Chaim 551: 16). The halachah does not follow the opinion of the Ran (Ta’anis 9b s.v. Gemara), who maintains that the Gemara omitted bathing during the Nine Days purposely.
 This, in fact, is the lashon used in Ma’adanei Shlomo (on Moadim, Bein HaMetzarim pg. 56).
 Aruch Hashulchan (Orach Chaim 551: 37).
 Tosafos (Brachos 16b s.v. istanis), Tur and Shulchan Aruch (Yoreh De’ah 381: 1 & 2). See Mishnah Berurah in Biur Halachah (554: 15 s.v. sichah & Shaar HaTziyun 38) who says this explicitly, and avers that on Tisha B’Av itself it is technically permitted. The Vilna Gaon (Biur HaGr”a, Orach Chaim 614, 1; Yoreh De’ah 381: 3) cites proof to this from the Yerushalmi Ta’anis (Ch. 1 Halachah 6). The Mishnah Berurah adds that it’s so obvious that this is permitted during the Nine Days (including Tisha B’Av), that there was no need for the Shulchan Aruch to even make mention of it. Although the Shulchan Aruch only explicitly mentions the phrase “leha’avir es hazuhama” regarding the prohibition of ‘sichah’, anointing, nevertheless, it is obvious that it applies as well to washing, which is a lesser form of ‘ta’anug’ than anointing. See also Levush (Orach Chaim 614: 1), Shulchan Aruch Harav (Orach Chaim 614: 1), and Yeshuos Yaakov (Orach Chaim 613: 1).
 Rambam (Hilchos Ta’aniyos Ch. 5: 6; “u’kvar nahagu Yisroel shelo le’echol bassar b’Shabbos zu v’lo yichansu l’merchatz ad sheya’avor haTaanis”), Ramban (cited by the Kaf Hachaim, Orach Chaim 551: 186), and Yeshuos Yaakov (Orach Chaim 551: 3). A similar shittah is widely quoted as the opinion of Rav Yosef Dov (J.B.) Soloveitchik zt”l in the name of his father, Rav Moshe zt”l, citing precedent from the Shach (Yoreh Deah 381: 1) and Aruch Hashulchan (ad loc. 3), that nowadays the prevailing minhag is to allow cold showering for a mourner in Shloshim. Therefore, it stands to reason that according to the Aruch Hashulchan’s understanding of the Shach’s position, one may do so as well during the less stringent Nine Days. [For example, see Nefesh HaRav (pg. 198) and sefer Shiurei HaRav al Inyanei Aveilus V’Tisha B’Av (pg. 21: 11; thanks are due to Dr. Moshe Simon-Shoshan of Bar-Ilan University for providing this valuable source); although it seems to be a matter of debate amongst the Rav’s Talmidim whether or not this drashah was merely expressed derech halimud or as actual psak lemaaseh, especially as it is not listed in the recently published Mesorat HaRav Kinot in the "Halakha Guide, Digest of Tisha B'Av Laws" as per the Rav’s Hanhagos, but rather stating simply that "the general custom is to forbid bathing for pleasure during the Nine Days" (pg. 786: 9).] However, the Rav’s noted talmid, Rav Michel Shurkin (Harerei Kedem vol. 2: 139 s.v a”h; pg. 286 - 287), points out that according to Rav Akiva Eiger and the Dagul Mervavah (ad loc.), the Shach was only referring to granting a dispensation allowing a mourner to wash his face, hands, and legs in cold water, and not a full bath. Ergo, he explains, this same hetter is what would apply as well to the Nine Days, and not a blanket hetter for a cold shower that many opine Rav Soloveitchik was proposing. Additionally, as a counter point, it is important to note that the basic understanding of the Rema (ad loc. 1) is to proscribe cold showers for a mourner in Shloshim, and many poskim, including the Taz (ad loc. 1), Teshuos Chein (Shu”t 31), Pischei Teshuva (ad loc. 2), Atzei Levonah (ad loc.), and Chida (Birkei Yosef ad loc. 1) follow his shittah. Moreover, the Rema’s psak is leshittaso, as in Hilchos Tisha B’av (O.C. 551: 16) he rules similarly - that one may not wash his whole body even in cold water during the Nine Days, based on the Terumas Hadeshen (vol. 1: 151), who avers that one should not simply take a cold bath or even a dip in the river during the Nine Days without pressing need. Therefore, practically, in this author's opinion, it seems not so simple to rely exclusively on this hetter and its comparison with a mourner.
 Shulchan Aruch (Orach Chaim 613: end 1), Mishnah Berurah (ad loc. 2; based on the Levush, Magen Avrohom, Elyah Rabbah, and Ma’amar Mordechai - Orach Chaim 614: 1).
 The Mishnah Berurah (613: Shaar HaTziyun 4), nevertheless explicitly permits ‘bathing to remove dirt’ on Yom Kippur, as even the machmirim (including the Bach, Taz, and Pri Chodosh - Orach Chaim 613: 1, and Matteh Efraim 613: 2) would agree that that is permitted on Yom Kippur. See also Shu”t Divrei Yatziv (Orach Chaim vol. 2, end 237, 4, s.v. u’lfee), who maintains that it is possible that there is no real dispute here, as all would agree that for a simple light sweat, any bathing would be assur as it would still be considered for pleasure, while for heavy sweat and grime all would agree that bathing would be strictly for hygiene and thus, permitted.
 Chayei Adam (vol. 2, 133: 19), Ben Ish Chai (Year 1, Parshas Devarim 16), Kitzur Shulchan Aruch (122: 13), and Mishnah Berurah (551: 97).
 Rav Moshe Feinstein’s opinion is cited in Rabbi Shimon D. Eider’s A Summary of Halachos of The Three Weeks (pg. 13: 7) as well as in Mesores Moshe (vol.1, Bein HaMetzarim, pg. 171, 367: 3). Rav Yosef Eliyahu Henkin’s shitta is printed in his approbation to sefer Nechamas Yosef, in his essential Ezras Torah Luach (5776; Chodesh Av pg. 121) and in his recent posthumously published Shu”t Gevuros Eliyahu (vol. 1, Orach Chaim 37: 4 and 153: 2). See also Shu”t Rivevos Efraim (vol. 3: 350 & vol. 4: 139) for a similar assessment. However, Rav Yechiel Michel Tukachinsky (Luach Eretz Yisroel, Chodesh Av, Parshas Devarim), the Chazon Ish (cited in Orchos Rabbeinu vol. 2, pg. 134: 18; although he maintains that nowadays one should not wash legs with hot water as people generally have their feet and legs covered), Rav Shlomo Zalman Auerbach (Ma’adanei Shlomo on Moadim, Bein Hametzarim pg. 56; he is also cited as expressing amazement that there are people who are scrupulous about showering daily and sometimes twice a day!), and Rav Yisroel Yaakov Fischer (Halichos Even Yisroel, Hilchos Bein Hametzarim, pg. 350: 1) are quoted as not agreeing with this chiddush, and maintaining that on Erev Shabbos Chazon one still should not bathe ‘kol gufo b’chamin’, following the Aruch Hashulchan (Orach Chaim 551: 36) and Mishnah Berurah’s ruling (ad loc. 95) regarding one who bathes in hot water every Erev Shabbos.
 If one is unsure if or when this is relevant to himself, he should ask his spouse, friends, or the guy davening next him in shul! Remember, Mitzvos Bein Adam L’Chaveiro constitute half of the Aseres HaDibros! Indeed, this author has heard b’shaim Rav Ezriel Auerbach that if one refuses to shower or take care of personal hygiene during the Nine Days and it is “shterring” others in their learning or davening etc., he is considered a ‘mazik’.
 Sha’arim Metzuyanim B’Halachah (vol. 3, Ch. 122: 12 & 13).
Although the first real showers, with plumbed-in water, were invented by the ancient Greeks, as after exerting themselves in the stadium, ancient Greek athletes would freshen up in the kind of shower depicted on an Athenian vase of the fourth century B.C.E., nevertheless, they were not common nor widespread until fairly recently, as showers were not deemed necessary until the monumental breakthrough by famed French chemist Louis Pasteur ignited the eventual discovery of germs. With the presence of germs and bacteria confirmed, new steps were taken in hygiene to prevent these germs from proliferating, sickening, and spoiling.
 Including Shu”t Salmas Chaim (New Edition, vol. 1: Orach Chaim 313), Luach Eretz Yisroel (Chodesh Av, Parshas Devarim; “velo rochtzin rechitzah shel ta’anug”), Shu”t Igros Moshe (Even Ha’ezer vol. 4: 84, 4),Halichos Shlomo (Moadim vol. 2, Ch. 14, Dvar Halachah 24), Ma’adanei Shlomo (on Moadim, Bein Hametzarim, pg. 55 and 56), Emes L’Yaakov (on Shulchan Aruch pg. 225, Orach Chaim 551, footnote 514), Shu”t Divrei Yatziv (Orach Chaim vol. 2, 237: 4), Ashrei Ha’Ish (Orach Chaim vol. 3, pg. 469: 36), Shu”t Shevet Halevi (vol. 7, 77: 2, 2 & vol. 8: 127), Shu”t Ohr L’Tzion (vol. 3, Ch. 27: 5), Shu”t Teshuvos V’Hanhagos (vol. 2: 260 and vol. 4: 129), Shu”t Yabea Omer (vol. 5, Orach Chaim 41), Shu”t Yechaveh Daas (vol. 1: 38), Rav Mordechai Eliyahu’s Darchei Halachah Glosses to the Kitzur Shulchan Aruch (122: 19), Sha’arim Metzuyanim B’Halachah (vol. 3, Ch. 122: 12 & 13), Shu”t Rivevos Efraim (vol. 3: 350; vol. 4: 139; and vol. 5: 377, 10), Shu”t Vayevarech Dovid (vol. 1: 74), Shu”t Shulchan Halevi (vol. 1, Ch. 16: 1, pg. 150), Yalkut Yosef (Kitzur Shulchan Aruch, Orach Chaim 551, Dinei Shavua Shechal Bo Tisha B’Av, 13), and Shu”t Siach Nochum (Orach Chaim 34). See also Rabbi Shimon D. Eider’s A Summary of Halachos of The Three Weeks (pg. 12: 4) [also cited in Mesores Moshe (vol. 1, Bein Hametzarim, pg. 171: 367)], who cites Rav Moshe Feinstein zt”l as ruling that one who is ‘metzta’er’ may even immerse himself for a short time in a swimming pool to accomplish cleaning oneself from perspiration and grime during the Nine Days. Rav Ovadiah Yosef zt”l several years ago reiterated his stance publicly on Israeli radio, that one should shower for hygienic reasons during the Nine Days. Additionally, Rav Yisroel Yaakov Fischer zt”l (Shu”t Even Yisroel vol. 9, Haaros on Mishnah Berurah, Hilchos Tisha B’Av, pg. 111) proves that regarding the Nine Days’s restrictions, any time ‘rechitzah’ is actually allowed (although he personally was generally very machmir regarding ‘rechitzah’ in the Nine Days; see next footnote), ‘sichah’ would be as well, and using soap and shampoo in a shower cannot be construed as more than ‘sichah’. See also Shu”t Emek Hateshuva (vol. 1: 92, 2) who applies similar logic to permit toothbrushing and floor cleaning (sponja) during the Nine Days; since they are meant for hygiene and cleanliness and not pleasure, they are likewise permitted. Interestingly, Rav Meir Brandsdorfer zt”l (Shu”t Knei Bosem vol. 1: 32) addresses the issue that the Mishnah Berurah (551: 93, quoting the Levush ad loc. 15) implies that this dispensation is only for children who medically need it; he concludes that that Mishnah Berurah’s allowance only theoretically applies to the general issue of ‘rechitzah’ for pleasure during the Nine Days. However, practically, if the ‘rechitzah’ is to remove sweat and grime, and certainly if it is for ‘refuah mammash’ [as mentioned by the Knesses HaGedolah (Haghos on Beis Yosef ad loc. 23), Elyah Rabbah (ad loc. 35), Shaarei Teshuva (ad loc. end 37), and Ben Ish Chai (Year 1, Parshas Devarim 15)] it is ‘pashut’ that one should not be stringent, as regarding Tisha B’Av itself, even an adult may technically be lenient to shower under those conditions (as previously mentioned in footnote 7).
 It must be noted that the Chazon Ish and Steipler Gaon were quoted (Orchos Rabbeinu vol. 2, pg. 133: 15; new edition 5775, vol. 2, pg. 165: 16) as being very stringent with showering during the Nine Days, even for hygienic reasons, and even though most other Rabbanim were mattir. They do allow pouring cold water on one’s back as a way to cool off, though. [Interestingly, Shu”t Rivevos Efraim (ibid.) cites differing views as to the Chazon Ish’s psak, with one opinion maintaining that the Chazon Ish ruled leniently for Bnei Torah to take a cold shower during the Nine Days since they could not properly concentrate on their learning due to their heavy sweating.] Rav Binyamin Zilber (Shu”t Az Nidberu vol. 11: 48, s.v. siman 350) rules stringently as well regarding showering (unless perhaps for a married woman). He adds that this is the Chazon Ish’s true shittah, and not as one of the opinions cited in the Rivevos Efraim quoted him as holding. He concludes ‘u’kdai ketzas lehitzta’er al seraifas Beis Elokeinu’. This is also Rav Chaim Kanievsky’s ruling (see Moadei HaGra”ch 334 and Orchos Rabbeinu ibid.), citing the Chazon Ish’s precedent. Interestingly, this exact case, of a Ben Torah in Bnei Brak during the Nine Days, is one Rav Shlomo Zalman Auerbach expressly permitted (Ma’adanei Shlomo on Moadim, Bein Hametzarim, pg. 55 and 56), explaining that a place as hot and humid as Bnei Brak is considered ‘ee efsher b’lav hachi’, impossible to go without’ (referring to at least a cold shower). Additionally, Rav Moshe Sternbuch (Shu”t Teshuvos V’Hanhagos ibid.) questions Rav Chaim Kanievsky’s shittah, as halachically the Nine Days restrictions cannot be any more severe than an actual mourner. Rav Nissim Karelitz (Chut Shani on Yom Tov and Chol Hamoed, Kovetz Inyanim pg. 346) takes a middle-ground Bnei Brak approach, maintaining that optimally showering is prohibited, even for one who is ‘mazeeyah’. Yet, if one is completely ‘covered in sweat’ and cannot handle it, or is suffering extreme discomfort and / or has a ‘reiach ra’, he may then take a cold shower. Rav Yisroel Yaakov Fischer (Halichos Even Yisroel, Hilchos Bein Hametzarim pg 340 - 341: 5, 9 and 10) writes similarly that sweat alone should not be enough to allow a shower dispensation, even for a bachur in Bnei Brak. However, if he is metzta’er harbeh and would put this rechitzah into the category of ‘refuah’, then it would be permitted, and even with soap, as the sichah prohibition is linked to the rechitzah prohibition.
 Halichos Shlomo (ibid. footnote 61).
 See Mishnah Berurah (549: 1), based on the Rambam (Hilchos Ta’anis Ch. 5: 1).
 Kaf Hachaim (Orach Chaim 551: 1; quoting the Yafeh Lalev vol. 2: 1).
 Midrash Rabbah (Shemos, Parshas Bo, Ch. 15: 21). See also the Gemara at the end of Maseches Makkos (24a - 24b), Gemara Ta’anis (30b), and Shulchan Aruch (Orach Chaim 554: 25).
Disclaimer: This is not a comprehensive guide, rather a brief summary to raise awareness of the issues. In any real case one should ask a competent Halachic authority.
L'iluy Nishmas the Rosh HaYeshiva - Rav Chonoh Menachem Mendel ben R' Yechezkel Shraga, Rav Yaakov Yeshaya ben R' Boruch Yehuda.