Mikvaos, Chapter 1, Mishnah 1. Before we enter the Mishnah itself, we need to lay out the foundation of the entire masechta, because this first Mishnah presumes it.
Parshas Shemini enumerates a long series of tumah sources, things that impart spiritual contamination to people and to objects. In the midst of that list the Torah inserts a key exemption: a ma'ayan, and likewise a bor holding a gathered body of water, yihiyeh tahor. Such waters stand outside the reach of all those sources of tumah the Torah has just enumerated, and their taharah is permanent, never subject to change.
The two subjects of the masechta
Masechtas Mikvaos revolves around this pasuk in its two applications. First, that these waters themselves do not become tamei. Second, that they are metaher: a person, a vessel or an object that became tamei is purified by immersion in them.
The pasuk names two kinds of water that purify. One is a ma'ayan, a spring: water that has collected deep beneath the surface and emerges from the ground on its own. The other is a bor mikveh mayim, a pit or ditch in which rainwater has gathered. The two share properties, but they are not identical, and the Torah hints at this with the word "ach", "only a ma'ayan." That exclusive expression singles out the ma'ayan and teaches that in certain respects its laws are more lenient than those of a mikveh.
Where they are alike
Two features are common to both. The first is that the water must be in the ground and not in a vessel. Immersion inside a k'li is not a valid tevilah, and water gathered in a k'li, even pure rainwater, does not purify a person.
The second is that the gathering must happen naturally. Rain falls and collects on its own in the hollow in the earth; the spring rises on its own out of the earth. Should human involvement intrude, for example if someone catches the rainwater in a vessel and then empties it into the pit, the mikveh is invalidated. Such water is called mayim she'uvim, drawn water. The Rishonim argue whether this disqualification of a mikveh composed of mayim she'uvim is a Torah law or a rabbinic enactment.
Where they differ
There are two fundamental distinctions between spring water and gathered rainwater.
- A ma'ayan purifies b'chol shehu, in whatever quantity it contains. It requires no measure of forty se'ah. So long as the entire surface of the person or object immersing is covered by the water, that is a valid tevilah, and there is no need to establish that forty se'ah are present. A mikveh, by contrast, requires forty se'ah, certainly for the immersion of a person, and rabbinically for the immersion of vessels as well.
- A ma'ayan purifies b'zochlin. The word zochlin describes water in motion, water that is flowing or trickling away, and a spring purifies even in that state. A mikveh purifies only b'ashboren, when the water is standing still.
The revi'is that never disappeared
Notice that the Torah never described the mikveh as containing forty se'ah. On the level of Torah law a mikveh is valid to purify vessels even with a mere revi'is of water. That small amount already carries the status of a mikveh: it is not susceptible to tumah, and vessels immersed in it become tahor. The Chachamim, however, annulled the shiur of a revi'is for the immersion of vessels; they would not permit immersion in so minimal a quantity, and required forty se'ah even for keilim.
But as this first perek will show us, the Chachamim did not erase the halacha of a revi'is entirely. Wherever we find a gathering of rainwater in the ground amounting to a revi'is, it still retains the mikveh's basic property: it does not become tamei.
The Mishnah: six levels
The Mishnah opens: "Sheish ma'alos b'mikvaos, zu l'ma'ala mi'zu." There are six grades in the laws of mikvaos, each one standing on a higher rung than the one before it. Every level has a greater degree of validity than the level beneath it.
The lowest of the six is mei geva'im. This refers to water sitting in a small depression or crevice in the ground, rainwater that gathered there on its own. Rain fell and filled a little hollow, and there is certainly no forty se'ah in it.
Such water is not susceptible to tumah while it remains in the ground. Only once it is removed from the earth deliberately, with intent, does it become nitlash, uprooted from the ground, and from that point onward it can indeed become tamei. Until then it is treated like a mikveh and does not receive tumah.
However, since it does not hold forty se'ah, it has no power to purify tamei water that falls into it. Consequently, whenever there is a concern that some tamei water has entered the hollow, we must picture the situation as follows: the original mei geva'im are not susceptible to tumah, yet somewhere within them lies a drop, perhaps only a drop, of water that is tamei, water that will go on to convey tumah to other things once it is removed from the ground. That drop is not neutralized in the mei geva'im.
Case one: a tamei person drank, then a tahor person drank
"Shasah tamei." A tamei person drank from the water of the hollow. The water that entered his mouth was rendered tamei by him, and when he drank, some of it remained on his lips and dripped back into the pit. That droplet, or perhaps slightly more, has re-entered the water as tamei water, and it is not nullified within the mei geva'im.
"V'shasah tahor, tamei." Should a tahor person now come and drink from that same water, he contracts tumah. His act of drinking constituted tolesh l'ratzon, an intentional lifting of water out of the earth, and we have to reckon with the possibility that the tamei droplet came up in his mouth together with everything else he swallowed. All the water he raised in that mouthful therefore became tamei.
Just how does the drinker himself turn tamei? Through a rabbinic decree, one of the eighteen gezeiros the Gemara catalogues at the opening of Masechtas Shabbos (yud gimmel, amud beis): shoseh revi'is mashkim temei'im, whoever swallows a revi'is of tamei liquids becomes tamei in his own body and may no longer eat terumah.
Case two: a tamei person drank, then water was drawn with a tahor vessel
"Shasah tamei, u'milah bichli tahor, tamei." The tamei man drank from the crevice, and afterward a second person filled a vessel that was tahor from that very hollow. The vessel contracts tumah. The reason is the same residue we have been tracking: a bit of moisture returned from the drinker's lips into the water and is lying there as tamei water, so when the water is scooped up into the vessel, the vessel is rendered tamei along with it.
Case three: a tamei person drank, then a loaf of terumah fell in
"Shasah tamei, v'nafal kikar shel terumah." A tamei person took a drink from the hollow, and subsequently a kikar, a loaf baked from terumah, tumbled into that water. On this case the Mishnah draws a line: "im hediach, tamei." Should he have washed the loaf off in the water of the crevice, the loaf becomes tamei.
Why? The loaf that got wet merely by falling in does not become tamei, because the water was not uprooted from the ground with intent. But once he performed an act of hadachah, actually rinsing the loaf by sloshing the water about, he has lifted the water up deliberately, and now that residual droplet left behind by the tamei person who drank is able to render the rest of the water tamei, and through it the terumah.
"V'im lo hediach, tahor." Where no rinsing took place, the terumah keeps its taharah, wet though it may be. True, in retrieving the loaf he brought up whatever moisture clung to it, but nothing there was raised with intent: it would have been perfectly fine with him had that liquid stayed down in the hollow. Water taken up in such a fashion does not become tamei, and the loaf of terumah stays tahor.
This is the first and lowest of the six levels: water that cannot become tamei while it rests in the ground, yet lacks the volume to nullify tumah introduced into it, so that a single deliberate removal of water can carry that tumah outward.