One of the Rabbinic prohibitions of Shabbos is that one may not bathe their body in hot water. This is referred to as גזירת מרחצאות and it applies even if the water was heated up before Shabbos. The reason this Gezeira was introduced was in response to unscrupulous bathhouse attendants, who would heat up water on Shabbos and say that it had been heated before Shabbos.
The prohibition also applies to bathing the majority of the body either at one time or limb by limb. One may wash minor isolated parts of their body (e.g. hands, feet and face) with water that was heated before Shabbos. Even though the Gezeira only applies to hot water, it is accepted custom amongst Ashkenazim not to bathe in cold water either.
The Poskim discuss whether the Gezeira on bathing in hot water applies to immersing in a Mikva as well.
Many Chassidim have the custom (based on the teachings of the Ariza”l) to immerse in a Mikva on Shabbos for extra Kedusha. This discussion is also relevant for a woman whose Leil Tevila falls on Shabbos evening.
Temperatures
Before discussing the approaches of the Poskim, we must first define the temperature categories that are discussed in relation to this Gezeira. There are 3 categories;
חמין (Chamin) - Hot water
פושרין (Poshrin) - Lukewarm water
צוננין (Tzonenin) - Cold water. This includes cold water which has been heated slightly to take off the chill (להפיג צינתן) but not to warm it substantially.
The Gezeira against bathing certainly applies to hot water. There is a dispute about the status of lukewarm water פושרין. Lemaaseh we are stringent to not bathe in lukewarm water either.
Three Approaches on Mikva
The Strict Approach:
The Chacham Tzvi rules that immersion has the same status as bathing. Therefore one may not immerse in a hot Mikva on Shabbos. Even using a lukewarm Mikva (פושרין) is forbidden since warm water is also subject to the Gezeira. If a woman’s immersion is scheduled for Shabbos evening the Chacham Tzvi advises that she should either use cold water or postpone immersion until after Shabbos when hot water may be used. When using a cold Mikvah, some hot water may be added to it in order to take off the chill.
A Rov should carefully weigh up his Psak as taking a strict approach may discourage women from going to Mikva.
The Lenient Approach:
The Korban Nesanel writes that immersion in a Mikva was never included in the Rabbinic Gezeira against bathing. Therefore immersion in a hot Mikva on Shabbos is completely permissible.
The Intermediate Opinion:
The Noda Biyehuda writes that one should not rely on the lenient ruling of the Korban Nesanel because he does not give a reason for the distinction that he draws between bathing and immersing. Therefore a hot Mikva may not be used on Shabbos. However, unlike the Chacham Tzvi, the Noda Biyehuda permits immersion in a lukewarm Mikva (פושרין). In his view only hot water (חמין) was included in the Gezeira. The Noda Biyehuda would instruct the Mikva attendants to add the hot water to the Mikva early enough on Friday afternoon so that by the onset of Shabbos the water would only be lukewarm.
Halacha
The Mishna Berura rules that those who warm up Mikvaos prior to Shabbos, should be careful to ensure that the water should only be פושרין (lukewarm) by the time Shabbos comes in. This is based on the ruling of the Chayei Adam. However, many Poskim adopt the lenient approach of the Korban Nesanel. They include; the Avnei Nezer, the Tzanzer Rov and the Klausenberger Rebbe. This ruling allowing the use of a hot Mikva on Shabbos is followed by Chassidim.
Igros Moshe discusses a fascinating case of a Mikva in his town, Luban in Communist Russia. The Mikva was heated by a non-observant Jew on Shabbos. In his Teshuvah Rav Moshe suggests the rationale of why immersion would be excluded from the Gezeira. Only bathing for cleanliness or for enjoyment was subject to the Gezeira. Since Mitzvos are not for personal benefit, immersion should be permitted in hot water (even in this case where the water was heated on Shabbos).
However in a later Teshuva, Igros Moshe rules that on Shabbos one may only use cold Mikvaos. If the only Mikva available for a woman is hot, she may use it and rely on the lenient Poskim rather than delaying her immersion.
Using a hot Mikva during Bein Hashemashos (the period of doubt between sunset and nightfall) is permissible according to all authorities. (This would only apply to men. Women may only ever immerse in the Mikva after nightfall).
“Hanging Out” in the Mikva
The Avnei Nezer writes that whilst immersing in a hot Mikva is permissible, delaying in the Mikva before or after immersing is certainly forbidden. Sitting in the Mikva more than necessary is for enjoyment and is no longer considered immersion but rather bathing which is forbidden. Rather one should enter the Mikva, immerse and exit.
Similarly, Lehoros Nosson rules that when immersing on Shabbos in a hot Mikva, only 1 or 2 immersions should be performed, even if one customariuly does more. Even in a cold Mikva one should limit their amount of Tevilos so as not violate the custom of not bathing in cold water.
Other Poskim allow one to do their regular number of Tevilos. All of these immersions are still considered part of the Mitzvah of immersion.
Extreme Heat
For Shabbos, the Mikva should not be heated above יד סולדת בו (approx. 40oC+) as this presents other Shaalos including the possibility of “cooking” should any cold water enter the Mikva.
