The source of tvilah, immersion, is complex. Interestingly, the Torah never states explicitly that a niddah, zavah, or a woman who has given birth has to immerse in order to become tahor, ritually pure, although it is assumed throughout the Talmud that this requirement exists and that it is Biblical. The Rishonim attempt to locate the source, and while Rambam (issurei Biah 4:3) states that it can be inferred from the fact that all ritually impure people in the Torah must go to the mikveh to become tahor, but Tosafot (Beitzah 11a, s.v. Lo Nitzrecha) rejects this approach and states that one cannot learn from general principles of ritual impurity, because it is possible that the requirements would be different when it comes to the woman’s status vis-à-vis her husband.
This debate points to an ongoing theme regarding the status of a niddah – a person who both has standard ritual impurity (like all of us today who are t’mei met – ritually impure due to contact or being in the same building with a dead body), and also a person who is forbidden to have sex. Is the latter status a dimension of the former, or something independent? Rambam certainly assumes these two statuses are combined, whereas Tosafot states they may be independent of one another. Thus, for Tosafot, it would have been theoretically possible to argue that a woman could not go to the mikveh, be a niddah for touching trumah, sanctified food, and the like, and still be permitted to her husband. In the end, obviously, a niddah must go to the mikveh to be permitted to her husband, but it is still an open question whether her two statuses are linked and whether this is the same tvillah of ritual purity and impurity. Earlier this year we saw a similar position of Ra’avad – supported by Ramban – who states that there are some circumstances (poletet shikhvat zera) that a woman’s shiva nikkiyim, seven clean days, would be interrupted only for ritual impurity, but not for her husband. Thus, according to Ra’avad, such a woman could go to the mikveh on day seven – ignoring this interruption – and be permitted to her husband, yet still be a full niddah regarding laws of ritual impurity!
Because the tvilah of a niddah and zavah is not mentioned in the Torah, there is uncertainty as to the requirements for the tvilah of a zavah. A zav, a man with an abnormal penile discharge, requires tvilah in mayyim chayyim – a natural well or spring. Is the same true about a zavah? Ramban in his commentary to Vayikra (15:19) states that according to the simple sense of the verses this is the case. And, in fact, there is a mishna (Mikvaot 5:5) that seems to imply this. However, the Tosefta (Megillah 1:14, Zavim 3:1) states explicitly that a zavah does not require mayyim chayyim. Now, this issue is never discussed explicitly in the Bavli or Yerushalmi, and hence there is some debate about how we rule. A number of Geonim were of the opinion that a zavah requires mayyim chayyim, and they went further to state that because of Chumrah d’ Rebbe Zeira, our current practice which does not distinguish between the status of niddah and zavah, all women must use a well or wellspring. This was a possible position to hold because many mikvaot in those times were exactly that – wells. However, all the Rishonim reject this position on the basis of the Tosefta, and certainly it would have made mikveh use impossible in communities which needed to use rainwater mikvaot. Of course, we rule this way, and almost all of our mikvaot are rainwater mikvaot. (So, also, were the mikvaot at Masada – but that was before Chumrah d’ Rebbe Zeira and hence only needed to be used for niddah purposes, not zavah).
When one realizes what women had to endure to go to the mikveh – climbing many feet down a deep dark well, and immersing in unheated water – we can only be inspired by their example of dedication and self- sacrifice. Of course, for men, the important message is not to feel a need to duplicate this, but to realize their responsibility to make mikvaot as welcoming, hygienic, and pleasant as possible – something that is feasible in rainwater mikvaot, and happens when sufficient attention and care is given.
In that vein, the Rishonim and poskim discuss going to the mikveh on Shabbat. They are bothered why this is allowed, since the general (Ashkenazic) practice is to not fully immerse oneself (in a pool, a bath, etc.) on Shabbat because of a range of Shabbat concerns (including, but not limited to, carrying the water on one’s body and squeezing the water out of one’s hair). They justify going to the mikveh on Shabbat either by recognizing that these concerns are not based on the Gemara, and hence in this case one can revert to the core halakha that such immersion is permissible, or by stating that the mitzvah of going to the mikveh at the right time overrides these concerns.
While this general Shabbat issue is largely resolved by the time of the Shulkhan Arukh, later poskim deal with another problem – going to a heated mikveh on Shabbat. Fully immersing oneself in preheated water on Shabbat is explicitly forbidden by the Talmud, and yet we do it in this case. How is that? A number of poskim reject the practice, but most attempt to find ways to justify it – sometimes by ingenious formal definitions (for example, the water isn’t hot enough to really be called hot). Rav Waldenberg (Tzitz Eliezer 6:20), after listing such formal distinctions, in the end states that it is possible that the value of not forcing a woman to delay going to the mikveh would override this rabbinic restriction. This is a powerful statement about how far we must go to make the mikveh as welcoming as possible, so that its physical state should never be the cause of anyone not going to the mikveh, or even delaying or hesitating using it.