Ohalos, Chapter 2, Mishnah 2. The chapter is busy listing the various forms of tumas meis that are metamei be'ohel, together with the shiur required for each one. Our Mishnah carries that list further, and it turns out to be a rich collection of disputes: how much blood of a meis is metamei, whether that blood may be gathered from more than one body, worms that emerge from the flesh of a meis, the ashes of a body that was burned, the dust of graves, and rakov that was kneaded together with water.
A Revi'is of Blood
The Mishnah begins with revi'is dam, a quarter of a log of blood. That measure may be familiar from the shiur of a kos of kiddush: it comes out to somewhere between three and five ounces. Where a full revi'is of blood left the body only after the person had already died, that blood is metamei be'ohel min haTorah.
Next the Mishnah adds u'revi'is dam tfusah, a revi'is of "gathered" blood. This refers to blood that flowed out at the very moment of death, as the neshamah was leaving: part of it came out while the person was still alive and part of it after he had died. Such a revi'is is metamei only mid'rabbanan. Practically, though, the halachah is the same in both cases: a person who is under one roof together with either a revi'is of blood that came out after death, or a revi'is of dam tfusah that came out at the time of death, becomes tamei.
From One Meis or From Two?
Here the Tanna Kamma adds a condition. The entire revi'is must have come mi'meis echad, from a single body. Rebbe Akiva disagrees: even blood collected from two different meisim joins together to make up a revi'is that is metamei be'ohel.
What stands at the root of this argument? It hinges on how one word in the Torah is treated. The pasuk forbidding contact speaks of "kol nafshos meis." As we pronounce it, the word is plural, nafshos, as though a vav were tucked in before the closing tav. But examine the letters that are actually written: nun, pei, shin, tav. Take away the nekudos, and a ba'al koreh who came to the amud unprepared would pronounce it nafshas, in the singular, and the tzibbur would be obligated to stop him. The Bartenura sets out the two sides. The Tanna Kamma maintains yeish eim lamasores: the halachah follows the written form of the word, and written that way it is singular, which teaches that the entire quantity of blood must originate in one body. Rebbe Akiva maintains yeish eim lamikra: the halachah follows the vocalized reading, which is plural, and therefore blood taken from two separate meisim may be combined.
Incidentally, the Bartenura notes the source of the word tfusah. It echoes the posuk in Yechezkel, "misboseses bedamayich," the very phrase joined there to "u'vedamayich chayi," the words we say at a bris milah: through the dam of milah come life and brachah.
The Blood of a Katan
Next in the list is dam katan sheyatzah kulo: a fetus whose full supply of blood came out. Rebbe Akiva rules kol shehu, that any quantity whatsoever is metamei. He learns this from the law governing a meis's bones. With bones, one who possesses rov binyano, the greater part of the body's frame, or rov minyano, the majority of its bone count, is tamei even without reaching the rova kav that bones otherwise require. Blood, reasons Rebbe Akiva, should be no different: once the whole of it stands before you, no measure needs to be met, even should the total fall short of a revi'is halog. This also accounts for the Mishnah's choice of a fetus as the case, a body at the very outset of its formation. In anything larger, it is hard to picture all of its blood together amounting to less than a revi'is.
The Chachamim disagree. Blood is metamei at a revi'is and not less, whatever its source. In their view it is simply not reasonable to say that every last drop left the body; some always remains behind. Since a complete quantity is never truly achieved, one cannot be metamei on the strength of "all of it."
A Kezayis of Rimah
The Mishnah now turns to kezayis rimah, an olive's volume of worms that formed from the flesh of a meis, bein chayah u'vein meisah, whether those worms are alive or already dead. Rabbi Eliezer is metamei kevisaro, treating them exactly like the flesh of the meis himself.
What moves Rabbi Eliezer to say so? Even a living person is sometimes called by the name rimah, as the posuk in Iyov says, "Af ki enosh rimah." The worm that emerges from a person's flesh carries the status of that flesh. Therefore, just as a kezayis of flesh from a meis is metamei, so is a kezayis of these worms, even while they are alive. The Chachamim, however, are metaher. True, the worm formed out of the flesh, but it is not that flesh; it has become its own living creature, and it does not carry the tumah of basar min hameis.
A Story in Bava Metzia
Here one is reminded of the celebrated Gemara concerning Rebbe Elazar, the son of Rebbe Shimon bar Yochai, in Bava Metzia, amud beis of daf pei daled. Rav Shmuel bar Nachmeni transmitted what he had heard from the mother of Rebbe Yonasan, who had it from the widow of that tzaddik: for a stretch of no less than eighteen years and no more than twenty two, he received no burial at all but lay in an upper chamber, and during that whole period his body showed no sign of decay. It was a nes, of the kind recorded about many tzaddikim. That same Gemara reports that he went on adjudicating monetary claims: the two parties would take their places at the entrance, each would lay out his side of the case, and a voice would emerge from within, identifying by name which of them bore the liability and which was in the right. Just how a neshamah in such a condition issues a psak is itself a marvel, and the whole passage deserves to be studied inside.
One day his wife noticed a worm emerging from his ear and was stricken with grief, fearing that the decay had begun. He appeared to her in a dream and reassured her: it was only because he had once heard a talmid chacham being shamed and had not protested as forcefully as he should have.
In the ordinary way of the world, of course, matters run as the posuk states: "tikvas enosh rimah." The Eibeshter's will is that the body go back to the ground, so that the neshamah may reach its perfection in the World to Come. Hence the Mishnah's inquiry into the status of such worms: Rabbi Eliezer maintains that living or dead they are metamei kevisaro, while the Chachamim rule them tahor.
The Ashes of a Burned Body
The Mishnah proceeds to eifer srufin, the ashes of a meis that was burned. Rabbi Eliezer says they are tamei, and their shiur is berovah, a quarter of a kav. In other words, a person's ashes are metamei with precisely the shiur that his bones would have been metamei. The Chachamim are metaher: the ashes are a new substance entirely and no longer a meis at all.
There are shitos, however, that the words "vachachamim metaharin" here are not absolute. Their intent is that a rova kav of ashes is tahor, but the ashes of an entire body would still be tamei.
Afar Kevaros
The Mishnah moves on to afar kevaros, the earth of graves. The Bartenura identifies it as soil that has absorbed a meis's blood along with his leychah, the fluid that seeps out of a body, and into which plaster has also become mingled. Regarding such earth the ruling is that melo tarvad ve'od is tamei. A tarvad is an oversized spoon, roughly a ladle, and the Mishnah calls for a ladleful together with a little more. The Bartenura supplies the reasoning: in a quantity of that size, it is not possible that a complete ladleful of genuine rakov is not contained within it, and it has already been established that melo tarvad of rakov, the dry matter into which a body crumbles, is tamei. Reb Shimon rules it tahor, but we are informed by the Bartenura that we do not pasken according to Reb Shimon.
Several Rishonim sketch the scenario in the following way. The accepted practice was to coat the burial niches hewn into caves with plaster. A meis would be set into such a niche, and as he crumbled away, bits of plaster from the surrounding wall worked their way into his dust. Now, it has already been established that rakov is metamei only so long as nothing extraneous is mingled with it. The Tanna Kamma confines that restriction to a situation in which the outside substance entered while the body was still in the midst of crumbling. Should it have been introduced only once the body had turned completely to dust, the admixture makes no difference and the dust retains its tumah. That is the basis for the Tanna Kamma's ruling: although plaster is unquestionably part of the mixture, it is nonetheless metamei. Reb Shimon draws no such line at all: regardless of whether the foreign matter arrived during the crumbling or afterward, once something else is mixed in, the whole is tahor.
Rakov Kneaded in Water
Finally the Mishnah teaches melo tarvad rakov shegvalo bemayim: one has a ladleful of rakov, the dust of a meis, and he kneaded it with water until it became like a dough. The ruling is eino chibur letumah. Being pressed into a single mass does not make it a single unit for the purposes of tumah. Consequently, if a person touches part of it he does not become tamei, since a full shiur is not present in what he touched, and likewise if he spreads over one portion of that dough as an ohel, he remains tahor. There is no complete tarvad of rakov in front of him, and the kneading does not fuse the pieces into one entity.
A Closing Thought
It is worth emphasizing yet again what all of this severity is telling us. If even the dust of a meis carries such powerful tumah, it is only because of the tremendous kedushah that filled the person while the neshamah was within him, and which has now departed. The Ohr HaChaim HaKadosh gives the mashal of a barrel that once held precious honey. Grind that barrel down to powder, and you will still find insects swarming over the remains to get at the honey that once sat inside. So too here: the tumah left behind is testimony to how exalted a person is while his neshamah dwells in him.