Ohalos, Chapter 9, Mishnah 4. This chapter follows a beehive (a caveras) that lies in the doorway of a house with its mouth facing outward, so that part of it is inside the house and part of it is outside, and it asks how tumah travels between the house, the beehive, and the space beneath the beehive. Our mishnah continues with a caveras that is not a functioning keli: it is defective in one of the two ways described earlier, either it has no openings in its side or it is broken, and therefore it carries the din of an ohel, which blocks tumah rather than passing it along. The one new detail added here is height.
The mishnah opens: "hoyso gevoyoh min ho'oretz tefach", the beehive was raised a tefach above the ground. It is not simply lying on the floor of the doorway with its opening pointing outside; there is a full tefach of empty space beneath it. That changes everything below, because a space of a tefach beneath a covering is itself an ohel, and an ohel spreads tumah from end to end.
Tumah beneath the beehive, or anywhere in the house
"Tumah tachteyho o babayis, tachteyho vehabayis tamei": should a kezayis of tumah be lying in the space below the outdoor portion of the beehive, or should it be resting somewhere within the house (any place other than the beehive's own cavity), the outcome is identical: the area under the beehive and the house alike contract tumah.
Why? Once there is a tefach of space underneath, the tumah does not stay in its own spot. It fills that entire sheltered space, and since the beehive reaches into the house, the tumah travels right in and the house becomes tamei. The same works in reverse: tumah lying in the house first fills the house, which is an ohel, then enters the space beneath the portion of the beehive that is inside the house, and from there, because there is a tefach of clearance, it immediately continues outward to the front of the beehive that sits outside the house. That outward spread reaches only the keilim in the space beneath the beehive; it does not travel any further.
And the mishnah adds: "tocho vegabo tohor", whatever is inside the beehive and whatever rests on top of it stay tohor. Since this caveras is not a keli, it functions as an ohel and holds the tumah back, so nothing that is under it can rise into it or onto it.
Tumah inside the beehive
"B'soicho, ein tamei ela toicho": when the tumah lies within the beehive, nothing beyond its cavity contracts tumah. The hollow of the beehive is an ohel in its own right, so whatever it shelters is tamei. But the tumah is sealed in: the sides have no perforations through which it could reach the house, and the ohel itself prevents any movement downward or upward.
Tumah on top of the beehive
"Al gabo, kenegdo ad horoki'a tamei": if the kezayis of tumah rests on top of the beehive, on the section outside the house, then everything in the direct column above it, straight up to the sky, is tamei, since nothing intervenes to stop the tumah. Everything else remains tohor. The beehive, being an ohel and not a keli, seals off the area beneath it, the interior stands as its own separate ohel, and there is no opening in the part of the beehive inside the house through which tumah could pass into the house.
Comparing this mishnah with the one before it
Both mishnayos are describing precisely the same beehive: one that fails to serve as a keli and is therefore treated as an ohel, holding tumah back instead of transmitting it. The single point of difference is clearance: in our mishnah a tefach of empty space separates it from the ground, in the previous one there was none. Let us set the four cases side by side.
- Tumah beneath the beehive. Without a tefach, tumah spread only in the column descending straight to the depths, and all the rest stayed tohor. With a tefach we fare worse: the whole area under the beehive contracts tumah, not merely the point directly below the kezayis, since that area now counts as an ohel that conducts tumah along its length. And because one end of the beehive reaches indoors, the house contracts tumah as well.
- Tumah in the house. Without a tefach, the house alone was tamei. With a tefach, the tumah fills the house, passes into the gap under the indoor section of the beehive, and from there runs across the entire underside to the outdoor end. The upshot: the house together with everything beneath the beehive is tamei, while the beehive's cavity and its upper surface remain tohor.
- Tumah inside the beehive. No change from the previous mishnah: the cavity alone is tamei. Clearance underneath makes no difference at all to this case.
- Tumah resting on the beehive outside the house. Again no change: the column rising directly above the tumah is tamei and nothing beyond it. What is happening below the beehive has no bearing on what happens over it.
Summed up in a line: the tefach of open space matters in only two of the four cases, tumah below the beehive and tumah in the house. In the first, the tumah now runs the full length of the sheltered space under the beehive, and because that beehive extends indoors, the house contracts tumah too. In the second, the tumah passes from the house into the gap beneath the indoor section and onward beneath the remainder. The upper surface and the cavity behave the same way with or without the clearance.
One further comparison deserves attention. In the perek's opening mishnah the caveras was intact and served as a keli, and since a keli presents no barrier to tumah, tumah lying below it rose upward through it. Here it is no keli at all, and that fact settles matters no matter what the clearance below may be: tumah under its outer portion leaves whatever sits on its upper surface tohor, and tumah on its upper surface leaves whatever lies below it tohor.