Mikvaos, Chapter 7, Mishnah 1. This mishnah and the one that follows deal with water in its various forms and stages: water that is frozen, water that has been altered or discolored, water that has had other substances mixed into it. The question in each case is the same: is this still considered water for the purposes of a mikvah, or has it lost that status?
The Mishnah opens by laying out three separate categories. There are liquids that are fit to raise the mikvah to its required measure and that also do not disqualify it. There are liquids that do disqualify the mikvah, through the halacha of three lugin of drawn water, and yet cannot be counted toward the forty se'ah. And there is a third group that neither raises nor disqualifies: even though the mikvah now physically holds more liquid, the halachic measure has not grown at all, and at the same time nothing has been ruined.
Ma'alin velo poslin
The Mishnah begins with the first category: "Eilu ma'alin velo poslin." These are the substances that can complete a mikvah which was short of forty se'ah, and which will never invalidate a mikvah even if they had first been gathered in a vessel. In other words, they are not subject to the disqualification of she'uvim, drawn water, at all.
- "Hasheleg," snow.
- "Habarad," hail.
- "Vehakfor," frost, water frozen in yet another form.
- "Vehagalid," the thin sheet of ice one finds at daybreak, once the dew has hardened over.
- "Vehamelach," salt, which itself originates from water.
- "Vetit hanorok," mud loose enough that it can be poured out of one utensil into another; precisely because it pours, its status as water remains intact.
All of these function exactly as rainwater does once they reach the mikvah, and even if along the way they were held in a receptacle they do not render the mikvah pasul and are not counted toward the three lugin of drawn water. The meforshim work through each item on the list and explain why each one escapes the status of she'uvim. We will not enter into those explanations here, but that is the settled halacha.
Rebbi Akiva's Report and the Testimony of the People of Medeva
The Mishnah now records a difference of opinion. "Omer Rebbi Akiva": Rebbi Akiva reports that when he presented this ruling about snow in the beis medrash, Rebbi Yishmael would rise and take the opposing side, "don kenegdi," holding that snow adds nothing to a mikvah's measure: "hasheleg einah ma'alah es hamikvah."
Then comes a second account: "He'idu anshei Medeva mishmo," the residents of the city of Medeva testified, quoting Rebbi Yishmael himself, that he had directed them, "tzu," go out, "va'asu mikvah," and fashion a mikvah entirely of snow, "bitchilah," from scratch, not merely as a means of topping off a pool whose measure was lacking. We are thus left with two contradictory traditions about what Rebbi Yishmael truly maintained.
Practically speaking, when a mikvah lacks its full measure and the only available means of supplying what is missing is snow or factory-produced ice, kerach mamlachti, the matter must be brought before a rav with genuine expertise in hilchos mikvaos. Such shailos call for a competent authority and are never to be resolved on one's own.
A further opinion follows, that of Rebbi Yochanan ben Nuri. He holds that "even habarad," a lump of hail, is "kamayim," to be treated as plain water. On his view, hail drawn into a vessel can invalidate a mikvah through three lugin, and it can equally supply a mikvah's missing measure when it arrives in a manner that is not she'uvim.
The Practical Case
Having listed the substances, the Mishnah asks the obvious question: "Keitzad ma'alin velo poslin?" Describe for us the situation in which these substances complete the mikvah's measure without ever disqualifying it.
The reply: picture a "mikvah sheyeish bah" thirty nine se'ah, in the Mishnah's phrase "arba'im se'ah chaser achas," one short of forty. "Nafal meihem se'ah letochah": a se'ah of one of the items on the list dropped in while still in that form, "vehe'elu," bringing the pool up to a full forty.
The Mishnah's seemingly repetitive wording, that the se'ah fell in and that it raised the measure, may be hinting at a point made by some of the meforshim: snow can appear to be more than it really is, since there are pockets of air trapped within it. The requirement is that the mikvah actually be brought up to a genuine forty se'ah, which may mean that somewhat more than a se'ah of snow is needed to accomplish it.
The closing words are "Nimtzu ma'alin velo poslin." It emerges that snow, hail and the rest of the list do bring a deficient mikvah up to its required measure, while never spoiling it, even where they sat in a vessel before reaching the water.