Ohalos, Chapter 3, Mishnah 4. The previous mishnah closed with a broad principle: kol shebameis tamei, everything that comes from a meis carries tumah, the flesh, the bones, the blood alike. The one exception is teeth, hair and nail, once they have been separated from the meis. Our mishnah opens with the word keitzad, "how so," and proceeds to show us in practical cases exactly how that rule plays out, and what happens when a part of the meis is connected to something that reaches into a house.
The First Case: The Meis Outside, His Hair Inside
"Hameis mibachutz use'aro bifnim": the body itself remains beyond the walls, and nothing but strands of his hair reach in beneath the roof. The mishnah's verdict is "habayis tamei": whatever is found inside that structure contracts tumah, no differently than had the corpse been lying stretched out on the floor within.
Why should this be? The ceiling spreads over those strands as an ohel, and the strands have not been severed from the body. Hair that has been separated transmits nothing at all. So long as it remains joined, though, it serves as a yad, a grip by which the meis is held. Consider how striking the picture is: not a single limb has crossed the threshold, and still a few hairs resting under the roof pull the tumah of the entire corpse indoors.
The Second Case: A Bone Bearing a Kazayis of Flesh
"Etzem sheyeish alav kazayis basar, vehichnis miktzaso mibifnim, vehabayis ma'ahil alav": there is a bone of a meis with a kazayis of flesh upon it, and a portion of that bone was brought inside the house, so that the house forms an ohel over that portion. The ruling is tamei.
A question suggests itself here: have we not learned that one lone bone does not spread tumah be'ohel? Quite so, yet this bone does not stand by itself. Resting upon it is a kazayis of flesh, and flesh of a meis in that quantity certainly does spread tumah be'ohel. The bone accordingly functions as a yad for the flesh, exactly as the hair in the earlier case functioned as a yad for the body.
Note how far this reaches: even if the flesh itself is entirely outside the house, and only a bit of the bone has come in under the roof, whatever is in the house becomes tamei. The handle brings in the tumah of what it holds.
The Third Case: Two Bones, Two Half-Zeisim
"Shtei atzamos va'aleihen kishnei chatzei zeisim, vehichnis miktzasam mibifnim, vehabayis ma'ahil aleihem, habayis tamei." Now we are given two distinct bones, and upon each of them rests half a kazayis of flesh. Part of each bone was inserted indoors, with the roof spreading over both as an ohel. The ruling: everything under that roof is tamei.
This is simply the earlier ruling applied twice over. Each of the bones is a yad for the portion of flesh it bears, and a yad brings along whatever it grips. The upshot is that the dwelling overshadows both of these half-measures of flesh, and two halves amount to a whole kazayis, which is precisely the quantity that conveys tumah be'ohel.
The Limitation: A Human Attachment Is Not an Attachment
At this point the mishnah sets a boundary. Suppose those two half-measures of flesh did not grow onto the bones of themselves, but were placed there by human hands, "hayu techuvim bidei adam." Then the verdict is tahor, and the mishnah supplies the governing rule: "she'ein chiburei adam chibur," whatever people fasten together does not count as fastened.
Understand why this matters here. The flesh itself, which is the source of tumah, is not in the house at all; only the bone has entered. The entire ruling of tumah rested on the bone functioning as a yad to the flesh. For that status the joining must be natural, the way flesh grows upon a bone. But flesh that a person stuck onto a bone, the way one skewers meat onto a spit for roasting, is not truly bound to it. Such a bone is no handle, and it will not carry the tumah of the flesh into a house when the flesh itself remains outside.
Reviewing the Three Cases
- Body outside, hair penetrating indoors: tamei. Severed hair transmits nothing, but hair still joined acts as a grip upon the corpse, so that the tumah of the whole body comes in along with it.
- A bone with a kazayis of flesh upon it, some of the bone indoors while the flesh stays outside, the roof overshadowing that portion: tamei, since the bone is the handle of the flesh, and matters are reckoned as though the flesh itself had entered.
- Two bones, each with half a kazayis upon it, part of each brought in beneath the roof: tamei, for every bone is the handle of its own half-measure, so the dwelling ends up overshadowing a full kazayis from a meis.
One reservation colors this entire discussion: a bone qualifies as a handle for flesh, able to render a dwelling tamei while the flesh lies outdoors, only where the two are bound together naturally. Where a person stuck the flesh onto the bone, the dwelling stays tahor, for "ein chiburei adam chibur," attachments produced by human hands carry no halachic status of attachment.