Ohalos, Chapter 15, Mishnah 10. This mishnah introduces a halacha which the Bartenura calls tumah bechiburin, tumah transmitted while the contact with the meis is still going on. And then, in what is really a second and separate din inside the same mishnah, we are taught something startling: a person's own hand, if it is large enough, can itself serve as an ohel over a meis.
A quick review of the levels of tumah
Before we can follow the mishnah, it pays to recall the foundations laid down when we began Keilim and again in the first perakim of this maseches. At the very top of the whole system stands the corpse: avi avos hatumah, tumah in its most potent form. Whoever comes into contact with it is thereby raised to the rank of av hatumah. (With a kli there is a difference, since a kli in contact with a meis can hold the status of avi avos hatumah itself, but our discussion now concerns a human being.) Suppose Reuven had contact with the corpse, and only afterward did Shimon lay a hand on Reuven: Shimon's level is no higher than rishon letumah.
These two ranks are worlds apart. One who is merely a rishon letumah carries his tumah until nightfall and no longer. An av hatumah, by contrast, remains tamei a full week, and he cannot reach taharah without being sprinkled with the water into which the ashes of the Parah Adumah were mixed.
What is tumah bechiburin?
Now to the halacha before us. Reuven lays his right hand upon a corpse. With that hand still in place, he reaches over with his left and makes contact with Shimon, or with a kli. What follows? Shimon and the kli do not slide down a rung to rishon letumah. Since Reuven had not yet broken his connection with the corpse, whatever he took hold of at that instant assumes the identical rank he holds: av hatumah. Contact with a man who is at this moment in contact with a corpse carries the same weight as contact with the corpse itself. This is what is called tumah bechiburin.
Ohel works no differently. Picture Reuven bent forward above a corpse, so that at this very moment he is absorbing tumas meis into himself by way of ohel. If, while he stands in that position, his hand rests on keilim or on another person, those keilim and that person likewise hold the rank of av hatumah and carry a seven day tumah, even though they are at a distance and never came near the corpse. Their tumah stems from contact with a man who is at this instant inside an ohel hameis.
The mishnah's cases
Our mishnah opens with "hanogeia bemeis venogeia bekeilim": a man has contact with the corpse through one hand while, at the same time, his other hand rests upon keilim. Then "hamaheil al hameis venogeia bakeilim": here one of his hands is stretched above the corpse, serving as an ohel, while the second hand is in contact with keilim. For both the mishnah rules "tmeiyin", the keilim carry tumas shivah, a tumah lasting seven days. We do not reason that all these keilim did was touch an av hatumah and that they therefore drop a rung. No drop occurs here at all.
The mishnah then sets against these a very different situation. "Maheil al hameis umeil al hakeilim": Reuven suspends one hand above the corpse so that it functions as an ohel, and at the same time suspends his second hand above keilim so that it forms an ohel for them as well. Nothing whatsoever is being touched: over the corpse there is a hand serving as ohel, and over the keilim there is a second hand serving as ohel. The mishnah adds "hanogeia bameis umeil al hakeilim", where one hand does lie upon the corpse itself while the second is stretched out above keilim as their ohel. For both of these the halacha is "keilim tehorim": the keilim stay tahor.
The great yesod: only a meis is metamei be'ohel
Why should this be? The reason is a truly fundamental principle. A person who has become tamei with tumas meis cannot transmit tumah by way of ohel, even while he is still in contact with the meis.
Take in how sweeping this is. Our entire maseches has revolved around tumas ohel: the beehives, the troughs, case after intricate case. Now the mishnah hands us a moyredike yesod: ohel functions only where the corpse itself, or a kezayis of its flesh, lies under that ohel alongside the person or the vessels that are contracting tumah. A man whose hand hovers above a corpse is indeed absorbing tumas ohel from it, yet he has no power to pass that tumah onward to a kli lying beneath him. True, one who makes contact with a corpse holds the rank of av hatumah, and whoever is in contact with him while that connection lasts holds exactly the same rank. But this is a law about contact, not about sharing an ohel with him. Nowhere do we find that a person picks up tumas ohel by standing beneath a man who has contracted tumas meis. The source of tumas ohel is the corpse, and nothing else.
Unless the man himself is the ohel
There is one exception, and here is where the hair is split. It is not that the kli receives tumas ohel because it stands under an ohel together with a man who became tamei from the meis. It is that the man himself can be the ohel over the meis. How? Very simply: his hand is very large.
Hence the mishnah's words: "im yeish beyadav posei'ach tefach, tmeiyin". Should each of his palms have the area of a square tefach, then when one of them is suspended above the corpse and the second above a kli, the keilim contract tumah. Follow the reasoning precisely. The kli has not become tamei on account of sitting beneath the ohel of some man who had contact with a corpse. It has become tamei because it and the corpse share one and the same ohel, and that ohel is the man.
Look more closely at that claim. In what way does this man qualify as an ohel? His palm covers a square tefach and it is spread out over the corpse. But the kli sits beneath his second palm, and the limbs running from the first palm to the second, namely his arms, may well be narrower than a tefach. At this point the mishnah gives us a special ruling: the two palms together constitute one ohel, for each of them holds the required square tefach, and both belong to a single body, which fuses them into one covering. So when a tefach sized palm is over the corpse and a second tefach sized palm is over a kli, that kli counts as sharing the corpse's ohel. Think of the hands as two wings of one roof, and one roof it is.
Putting it in perspective
Because this section really stands as a din unto itself, let us line up the whole picture:
- In the standard case the corpse holds the rank of avi avos hatumah. Reuven makes contact with it and thereby becomes an av hatumah. Should he afterward place his hand on Shimon or on a kli, they take on the lower rank of rishon letumah, tamei only until nightfall, while Reuven himself carries a week long tumah.
- Should he lay a hand on Shimon or on a kli before releasing his hold on the corpse, this is tumah bechiburin: no descent to rishon letumah takes place, and they too hold the rank of av hatumah.
- The same applies where Reuven's palm is stretched above the corpse and, in that very posture, he lays his other hand on keilim: such keilim carry a tumah of seven days.
- Where he touches nothing at all, however, and merely suspends a palm above the corpse while his second palm serves as an ohel above keilim (or where he lays a hand upon the corpse and stretches the other above keilim), the keilim stay tahor, since a human being who has contracted tumas meis is never a source of tumah through ohel. Only the corpse generates tumas ohel; a man never becomes such a source, not even while his hand rests upon it.
- The one exception: where each of his palms covers a square tefach, the man is himself the ohel. In that case the further kli or the further person is not deriving tumah from him whatsoever; the tumas ohel reaches it directly from the corpse, because the two of them are under a single ohel together.
Two houses and two half zeisim
The mishnah rounds off with an illustration that makes the principle vivid. "Shnei batim": two houses adjoin one another, their entrances facing the same way. "Uvehen kishnei chatzoi zeisim": lying inside them are two portions of flesh from a corpse, each amounting to only half a kezayis. Since half a kezayis falls short of the shiur needed to generate tumas ohel, as matters presently stand neither house has any problem.
Then a passerby arrives: "poshat es shtei yadav lahen", he thrusts a hand into the one house and a hand into the other. Rules the mishnah, "im yeish beyadav posei'ach tefach, meivi es hatumah": assuming each palm covers a square tefach, he has just carried the tumah from house to house. Both palms belong to one body and therefore make up a single ohel; the two half zeisim now find themselves sheltered beneath one covering, and both houses are tamei.
Imagine the fellow's surprise. He was strolling down the street, perhaps stretching his limbs, when someone catches hold of him: "Have you any idea what has just happened here? One hand of yours went into this house and one into that one, and there is a half kezayis sitting in each of them. Hold out your palms and let us measure. A full square tefach! You have turned the pair of them into a single ohel, and now both houses are tamei!"
"Ve'im lav, eino meivi es hatumah", and if his hands are measured and found to be less than a tefach, everyone may breathe easily. Hands that lack the measure of a tefach have no din of an ohel, and so they never joined the two houses together. Each house is left with its own separate half kezayis, and half a kezayis cannot create tumas ohel.
The lesson of this mishnah, then, is a sharp one: tumas ohel is generated by the meis and by nothing else, yet an ohel can be made of the most unexpected material, even a man's outstretched hands.