Ohalos, Chapter 13, Mishnah 5. Throughout this perek we have been studying the opening that measures a square tefach, the size through which tumah crosses from one side of a partition to the other. The mishnah before us supplies a list of objects: set any of them inside such an opening and the space no longer holds a full square tefach. The tumah then remains where it stands and does not travel into the room beyond.
Imagine a window, or simply a hole, in a wall, exactly a tefach in each direction. I take one of the items the mishnah is about to name and place it inside. The open air has shrunk, the required measure is gone, and the object functions as a chatzitzah, a barrier. Not every object qualifies for this job, and that is precisely what makes the list before us so remarkable.
Tamei Material That Still Blocks Tumah
Ordinarily an object that carries tumah itself cannot serve to hold tumah back. Yet the opening clause of the mishnah, which demands careful reading, says exactly that:
"Eilu mema'atin es hatefach: pachos mik'zayis basar mema'et al yedei rova atzamos."
Let us review the shiurim. Basar hameis, flesh of a niftar, in the amount of a k'zayis, is metamei in three ways: through maga (touch), through masa (carrying, even with no contact), and b'ohel (sharing a roof with it). Any amount below a k'zayis conveys nothing at all, and even one who touches it stays tahor.
Now the case. Inside one room of a house lie bones of a niftar in the amount of a rova kav (one fourth of a kav). The neighboring room holds keilim. The wall between the two rooms has an opening one tefach in each direction, and sitting in that opening is basar hameis in a quantity below a k'zayis. That morsel of flesh shrinks the opening beneath the necessary measure, and it therefore keeps the tumah of the rova of bones from reaching the keilim next door.
Switch the tumah in the room. Say the floor holds not bones but flesh of a niftar in the amount of a k'zayis, while my under-shiur morsel still sits in the window. Will it block? Not at all. The flesh in the window is mitztaref with the flesh on the floor, the two merge into a single quantity of tumah, and nothing is blocking anything. The entire mechanism depends on the tumah in the room being bones, because bones and flesh do not combine with one another for these halachos.
Here lies the irony. The object in the window really is flesh of a meis, and nevertheless, since it falls short of a k'zayis and since the tumah it faces is atzamos, it serves as a blocker.
The Mirror Image: A Bone Fragment Under a Se'orah
Flesh has its shiur of a k'zayis; a bone of a meis has a shiur of its own, a piece as large as a se'orah, a barleycorn. Hence "u'pachos mei'etzem k'se'orah mema'et al yedei k'zayis basar": a sliver of bone that does not reach the size of a se'orah, lodged in that square-tefach window, cuts the measure down and stops the tumah, on condition that the tumah in the room is flesh of a meis in the amount of a k'zayis. Since bone and flesh never join together, the sliver stays under its own shiur and bears no tumah.
Should the tumah in the room be bones, however, the sliver achieves nothing: it is mitztaref with them, and the two together add up to one tumah. So the pattern runs both ways: flesh under its shiur stops the tumah of bones, and bone under its shiur stops the tumah of flesh.
"Pachos Mik'zayis Min Hameis"
Next in the list: an amount below a k'zayis taken from a meis. On the face of it we have already learned this. The Bartenura explains that the second mention delivers an additional chiddush. Exactly as an under-k'zayis morsel of flesh restrains the tumah of bones, it likewise restrains other varieties of tumas meis: a revi'is of blood of a meis, for instance, or afar of a meis. The single restriction is that the tumah in the room may not be flesh, for then the two would merge. Provided the tumah opposite it is something other than flesh, and the morsel in the window is under a k'zayis, the opening drops below the measure and the tumah is held in place.
Neveilah, Sheretz and Food
"Pachos mik'zayis min haneveilah": neveilah in an amount that does not reach a k'zayis. A neveilah is a beast whose life ended other than through shechitah, and its shiur for tumah is a k'zayis.
"U'pachos mika'adashah min hasheretz": a dead sheretz in a piece smaller than an adashah, a lentil. Mishnayos Taharos has brought us to this subject repeatedly: eight species of sheratzim are metamei once dead, and the shiur of that tumah is a lentil's worth. Anything beneath that is not tamei, and it is therefore eligible to shrink the opening and detain the tumah. The two shiurim side by side: neveilah of a beheimah or chayah at a k'zayis, neveilah of a sheretz at an adashah. Beneath the shiur, the material carries no tumah and can bring the opening down.
"U'pachos mik'beitzah ochlin": food in a volume that does not reach a k'beitzah, the volume of an egg. Food in such a quantity cannot pass tumah on to anything else, and mid'oraisa it does not become tamei itself. It too, then, may sit in the window as a barrier.
Grain Reaching In Through the Window
"T'vuah shebachalon": grain in the window. The picture is charming. The grain is still rooted where it grows, outside the house, and its stalks have pushed inward and now occupy part of the window's open space. That brings the opening below the measure of a tefach.
An objection suggests itself: surely this is a great deal more food than a k'beitzah. The answer is that it remains joined to the ground, and whatever is attached to the ground is not mekabeil tumah in the first place.
The Tosfos Yom Tov contributes a subtle point. If the growth were sprouting from the wall itself, which does occur, the owner would tear it out, since such growth ruins a wall. Because we can be sure he will not tolerate it there, it cannot be counted as a chatzitzah. When it grows from the soil outside and its shoots have found their way into the window, he has no motive to remove it; he may well enjoy it. It will remain, it is not mekabeil tumah, and so it holds the tumah back.
A Web With Substance
The list goes on with "v'chochai", the web of a spider. The term is familiar from Hilchos Shabbos, where we are instructed to sweep the spiders' webs out of the corners of the house in honor of Shabbos.
The mishnah stipulates a web "sheyeish bah mamash", one possessing real substance. Webs are not all alike. Spiders come in an enormous variety of species; some spin threads so delicate that they have no staying power, while others weave something thick that genuinely looks like a piece of fabric. A web of that quality has enough reality to it to bring the opening under a tefach.
The Neveilah of a Tahor Bird
"Nivlas ha'of hatahor", in a case where "lo chishav aleha". The full sugya belongs to Maseches Taharos, and may the Eibishter grant us health and strength to arrive there, but the fundamentals are needed right here.
What is the halachah concerning a kosher bird that expired with no shechitah? One might suppose that every creature whose life ends without shechitah becomes tamei, but that principle governs a beheimah and a chayah. Birds are subject to an entirely separate set of halachos. A non-kosher bird that expired, an eagle or a hawk for example, has no tumas neveilah whatsoever. A kosher bird, a chicken let us say, that expired on its own is metamei b'veis habli'ah: when a person swallows a k'zayis of it he becomes tamei. It does not, however, transmit tumah by touch or by carrying.
There is a second avenue by which such a bird might become tamei, one that has nothing to do with tumas neveilah: the tumah that applies to food. For that it must count as food, which requires that it be located somewhere in which people do consume bird neveilos (clearly not Yidden, since a Yid may eat nothing that was not shechted). Only in a place where it is treated as edible does it acquire the status of ochel and become capable of receiving tumah the way any food does.
With that, our case is transparent. Before us is the neveilah of a kosher bird, a chicken that expired on its own, and no one ever gave a thought to eating it. Such a bird is a valid chatzitzah and brings the window under a tefach. Follow the lamdus here, which is geshmak: mah nafshach, take it either way. Which tumah could this chicken carry? Tumas neveilah? That comes about only through swallowing, and lying in a window it is neither swallowed nor conveying anything. Tumas ochlin? Nobody in that locale regards it as food. And so the mishnah's condition, that no thought was directed toward it, means that mimeila it is not mekabeil tumah, and it stands in the window as a barrier.
The Neveilah of a Tamei Bird
The last case of the mishnah: "v'nivlas ha'of hatamei shechishav aleha v'lo huchsherah, o huchsherah v'lo chishav aleha." A non-kosher bird that expired, as we clarified, bears no tumas neveilah at all. Its lone route to tumah is through the laws of food, and there two things are needed.
The first is machshavah: someone has to have designated it as food, in a locale where such things are eaten. The second is hechsher: it must have been touched by one of the seven mashkin. Food is not susceptible to tumah before it has been moistened by one of those liquids. (Produce carries the further condition of being severed from the ground; with a bird that question does not arise.) The siman for the list is "yad shachat dam": yayin, dvash, shemen, chalav, tal, dam and mayim.
The mishnah therefore supplies both halves: machshavah took place but no liquid ever reached it, or a liquid reached it but nobody thought of it as food. Either way it cannot become tamei, and mimeila it works to detain the tumah in the window.
A question presents itself. By the kosher bird the mishnah listed a single condition, that no machshavah was made, and said nothing regarding whether it was ever rendered susceptible. Why the discrepancy? Because although food in general cannot become tamei until it has been moistened at least once by one of the seven liquids, the neveilah of a tahor bird is exempt from that requirement, for reasons that will emerge in the coming mishnah. That is why, by the tahor bird, the mishnah raises only the question of machshavah: if no one considered it food, there is no tumah whatsoever, and it blocks the window.
Reviewing the Mishnah
The mishnah enumerated the items which, once placed in an opening, bring it beneath the measure of one tefach in each direction:
- Flesh of a meis that does not amount to a k'zayis holds back tumah when the tumah in the room is a rova of bones, since flesh and bone do not join together and this quantity has no tumah of its own. If the floor holds a k'zayis of flesh, though, the morsel in the window merges with it and accomplishes nothing.
- A bone fragment that does not reach the size of a se'orah holds back tumah when the tumah in the room is flesh of a meis, since bone and flesh do not join. Facing other bones it simply merges with them and no reduction is left.
- An under-k'zayis amount from a meis, repeated in order to teach that it is effective against any tumas meis other than flesh, such as a revi'is of dam hameis or afar of a meis.
- Neveilah in an amount short of a k'zayis; a dead sheretz in a piece short of an adashah; food in a volume short of a k'beitzah.
- Grain still rooted in the soil outside the house whose stalks pushed into the window, which is not mekabeil tumah and therefore blocks.
- A spider's web that has genuine substance to it.
- The neveilah of a kosher bird toward which no machshavah of food was directed, since its tumas neveilah operates only through swallowing and not through lying, touching or carrying, and as food it was never designated.
- The neveilah of a non-kosher bird, which has no tumas neveilah at all, in a case where machshavah was made but the moistening of the seven liquids is missing, or the moistening occurred but the machshavah is missing.
And as we established, the neveilah of a kosher bird needs no moistening by the seven liquids, so the only question there is whether anyone intended it for food. Tumas neveilah it does not carry; the sole shaylah is whether it ranks as food, and it ranks as food only where chishav aleha, where someone truly designated it as such.