Ohalos, Chapter 10, Mishnah 6. This chapter is occupied with the aruvah, the skylight or opening left in the roof of a house through which one can look straight up and see the sky. Our Mishnah adds a new element into that opening: a vessel standing on the floor of the house directly beneath the aruvah, and it asks how tumah travels once such a vessel is in the picture.
The case
"Aruvah shehi besoch habayis": a house whose ceiling contains an aruvah. "Ukedeirah nesunah tachteha": a kedeirah, an earthenware pot (kli cheres), sits on the floor squarely below that gap. The Mishnah takes pains to fix the relative sizes of the two. The opening is the larger, the vessel the smaller, and this is conveyed through a picture: "she'im ta'aleh", were the pot lifted straight up, it would travel through the gap and out into the open air, "ve'ein siftoseha nog'os ba'aruvah", without its lips so much as grazing the edges of the opening on the way through.
The first halachah: the pot resting on the floor
Now the Mishnah gives the din. If there is tumah, let us say tumas meis, a tumah that is metamei be'ohel, and it is found in one of three places: "tachteha", underneath the pot; "besocha", inside the pot; or "al gabah", resting in the air above the pot. In all three of these situations the rule is "tumah boka'as ve'olah, boka'as veyoredes". This is a phrase we have met before in this masechta: the tumah splits through and rises, defiling whatever lies in its path directly above it, and splits through and descends, defiling whatever lies in its path directly beneath it, but it does not spread off to the sides.
In practice, then, vessels standing elsewhere in the house stay tahor, and so does a kli laid over the aruvah at a spot that is not directly above the kedeirah. Since the opening exceeds the vessel in width, a kli can be spread across the aruvah to form an ohel while still lying outside the vertical line of the vessel, and such a kli is not rendered tamei.
A question on the kli cheres
Here a difficulty presents itself. We have learned again and again throughout Maseches Keilim that a kli cheres becomes tamei only from its inside, from its avir, and not from contact with its outer surface. If a dead sheretz touches an earthenware vessel on the outside, the inside stays tahor. So when the tumah lies beneath the pot, how does it reach the inside of the pot at all?
The Bartenura resolves this. Because we are dealing here with the din of tumah boka'as ve'olah, tumah that drives straight upward, it affects everything standing in its path automatically, and the interior of the kli cheres is in that path. Exactly how this mechanism works is a subject with a great deal of Torah in it, but this is the principle, and we will move on.
The second halachah: the pot raised a tefach
The Mishnah proceeds to a second scenario: "hoysah gevohah min ha'aretz tefach". Here the kedeirah no longer sits directly on the floor but stands at a height of a tefach or higher. In that case, should the tumah be located "tachteha", in the space below the vessel, "oy babayis", or somewhere else in the house, that is, beneath the house's ceiling rather than beneath the opening, the ruling is "tachteha vehabayis tamei": keilim in the space below the vessel and keilim anywhere in the house alike become tamei.
Why? Because a vessel standing at that height creates beneath itself a genuine ohel, the minimum dimensions of an ohel being a tefach by a tefach. That ohel is not something separate from the ohel produced by the house's ceiling; the two merge into one single ohel. Whatever lies below the kedeirah and whatever lies under the ceiling therefore occupy one common airspace and convey tumah to one another.
Yet in this very case the Mishnah rules "tocha vegabah tahor": the inside of the kedeirah and whatever rests on top of it stay tahor. The pot itself blocks the tumah from rising any higher.
Why does the pot block?
Why should that be? Turn to the Bartenura on the words "tocha vegabah tahor". He explains that the kedeirah is chotzetzes bifnei hatumah, it forms a barrier before the tumah, "umatzeles im dofnos ha'ohel", it rescues in partnership with the sides of the ohel. But what is meant by saying that the vessel rescues in partnership with those sides?
Bring to mind the rule of gud asik. Its familiar application is in hilchos sukkah: a mechitzah ten tefachim high is regarded as though it kept climbing until it reached the sechach, and the empty stretch above it, wide enough for a bird to fly across or a goat to leap through, is no objection at all. For certain halachos, in other words, we treat a partition as if it ran upward even when in reality it stops short.
The same applies to our kedeirah. Halachah regards its sides as continuing upward until they arrive at the aruvah, where they meet the ceiling of the house. It is that hypothetical linkage which empowers the vessel to serve as a chatzitzah and halt the tumah. Standing alone, this pot could never hold tumah back; it does so in partnership with the sides of the ohel, and that is exactly what the Bartenura intends. Hence, although the area beneath the vessel is tamei, the tumah never enters the vessel, and all the more so nothing above it is affected. The Tosfos Yom Tov here treats the matter at greater length: which pots hold back tumah and which do not, what sort of vessel is under discussion, and whether it is one that is mekabel tumah. The basic concept, though, is as described.
The third halachah: tumah inside or above the raised pot
The reason: tumah lodged within the vessel or resting upon it is boka'as veyoredes, breaking straight down. Having descended into the area below the kedeirah, and that area qualifies as an ohel in its own right because of the tefach of clearance, it then fans out sideways through the remainder of the house. In such a setup the vessel protects nothing whatsoever.
The reason is that tumah situated in the pot or above it is boka'as veyoredes, it cuts its way straight downward. Once it descends into the space beneath the pot, and that space is an ohel in its own right because the pot is raised a tefach, the tumah spreads out sideways into the rest of the house. In this configuration the pot saves nothing at all.
Chazarah
Let us go over it. A house has an aruvah in its ceiling, and a pot sits on the floor below it, the vessel being the smaller of the two, so that were it raised it would pass through the gap without touching its edges.
- With the vessel set directly on the floor, tumah found beneath it, within it, or above it pierces upward and downward alone, leaving whatever lies to the sides tahor.
- With the vessel standing a tefach high, the area beneath it constitutes an ohel that merges with the house. Tumah below the vessel or anywhere in the house therefore renders every kli below the vessel and every kli in the house tamei. Even so, its interior and whatever rests upon it remain tahor, since the vessel, treated as though it climbed upward and met the ceiling, bars the tumah.
- Should the tumah be within that raised vessel or upon it, nothing escapes: the tumah breaks downward into the space below, and from that ohel of a tefach it disperses throughout the house.
A closing observation. We invoked gud asik, envisioning a partition drawn upward. There is also a counterpart, gud achis, envisioning a partition drawn downward, and some learn our case along precisely those lines: rather than extending the vessel up to the ceiling, we bring the ceiling that surrounds the opening down, gud achis, until it reaches the vessel. Whichever image you prefer, the vessel rising or the ceiling descending, tumah lying below the kedeirah is prevented from climbing any higher. This is a genuinely geshmake sugya, one that could easily occupy hours of learning.