Ohalos, Chapter 15, Mishnah 7. Until now we have been dealing with houses that still have hollow space inside them, and with the way tumah travels from one part of such a house to another. Our Mishnah takes up a house whose owner has packed it solid and has no intention of emptying it out. The material here is not straw, which a person stores in order to feed his animals or to spread out for bedding, but earth and pebbles, and the owner declares in his heart that they are staying put. Once that is so, the Mishnah teaches, we are no longer looking at an ohel at all, and the rules of how tumah spreads change completely.
The cases of the Mishnah
"Bayis shemilo afar o tzroros u'vitlo": a house that a person filled with afar, with earth, or with tzroros, with pebbles. Tzroros is a word we have met before, in the sugyos of Keitzad HaRegel, where pebbles kicked up by an animal's foot are discussed. Unlike straw, which is stored with a plan to use it up, here the owner has been mevatel the fill: as far as he is concerned, this earth and these pebbles are now part of the house and will remain where they are.
"Vechein kri shel tevuah": and the same halachah applies to a kri, a pile, of grain. Kri is another familiar word. Throughout Seder Zeraim we encounter the principle that min haTorah a single grain of wheat is enough to exempt an entire kri from the obligation of terumah, chitah achas poteres es hakri. Here a person had a heap of grain and decided to leave it in place.
"O gal shel tzroros": or a gal, a mound, of pebbles, which he likewise leaves standing. At first glance this looks like a repetition, since a house filled with tzroros was already mentioned. What is gained by adding a mound of pebbles? The commentators cite the Rambam, who understands that these final clauses are not describing a house at all. On his reading the Mishnah presents two distinct scenarios: one is the house that was packed with earth or pebbles and whose owner was mevatel them there; the other is out in the open, a heap of grain or a mound of pebbles resting on the ground by itself, which its owner has decided never to move.
"Afilu k'galo shel Achan," the Mishnah continues, extending the halachah even to a heap of the sort that was piled over Achan. To grasp what is being added here, we need the incident recorded in Sefer Yehoshua.
Galo shel Achan
After Yericho fell to Klal Yisroel, Yehoshua issued an unmistakable warning that nothing inside the city might be touched. Achan disregarded it and helped himself to what had been captured. He was already a rich man, and riches have a way of sharpening a person's appetite for more. What had caught his eye? Chazal tell us that an avodah zarah stood in Yericho with a tongue made of gold, and before it hung a garment of enormous value together with a large sum of money, all of it presented by the anshei Yericho to their avodah zarah as a matanah. His yetzer hara got the better of him, he carried the whole lot away and buried it under his tent.
Achan had committed this sort of theft on earlier occasions, yet this was the first time since Klal Yisroel had crossed the Yarden, and from the crossing onward every Jew bore responsibility for his fellow. Shortly afterward the nation went to war against Ai, and there Yair ben Menashe was killed, a man whose worth was reckoned against the majority of the anshei haSanhedrin. The Yidden were broken by the defeat. Yehoshua rent his clothing, threw himself to the ground and poured out his heart before Hashem. The answer came back to him: why are you weeping? Yisroel has transgressed. A man was moel b'cherem; someone helped himself to booty that had been placed under a ban.
Yehoshua wanted to know the man's identity. Hashem responded that lashon hara is not something He engages in: cast a goral and uncover the offender yourself. Yehoshua turned to the choshen, where twelve stones stood for the twelve shevatim. All of them were radiating light, yet the stone belonging to Shevet Yehudah was visibly dimmer than the rest, and from this Yehoshua understood that the man had come out of Yehudah. A goral was then drawn among the members of that shevet, and Achan was singled out.
Yehoshua asked him for a confession, and Achan's first response was brazen. Moshe Rabbeinu has not been gone thirty days, he shot back, and you have already lost sight of the Torah's rule that al pi shenayim eidim o sheloshah eidim yakum davar. Are you going to convict a man on the strength of a goral? Draw lots between yourself and Elazar HaKohen, the generation's two greatest men, and the lot will land on one of you as well! The taunt caused Yehoshua tremendous agmas nefesh. Through ruach hakodesh he knew that a day would come when Eretz Yisroel would be apportioned by goral, and if Achan succeeded in casting suspicion on whether a goral genuinely expresses the will of Shomayim, that entire division would be undermined.
Yehoshua therefore said to him: ten kavod l'Elokei Yisroel, do not treat the goral with bizayon. The men of Shevet Yehudah standing nearby overheard the exchange and their anger turned against Yehoshua, while the remaining shevatim lined up behind him. Seeing that fighting was about to erupt, Achan concluded that admitting the truth was the wiser course. He acknowledged having taken from the captured goods, chatasi laShem, and that he had done the same on earlier occasions, back in Moshe's lifetime. His punishment was sekilah. Still, because he had been modeh, he was granted a chelek l'Olam Haba, a point alluded to in Yehoshua's words to him, "ya'achorcho Hashem bayom hazeh": the curse belongs to this day and not to the World to Come. Once he had been executed, a great mass of stones was heaped upon his body, and it stayed there until he was brought to burial. That heap is what is known as galo shel Achan.
Why there is no ohel here
Now we can hear what our Mishnah is teaching. Even a mound like galo shel Achan, which was destined to stand only until the tumah beneath it would be removed, still counts. One might have argued that such a pile is not truly bateil in its place, since everyone knows it is temporary. In all the other cases of the Mishnah the whole point is that the owner has resolved to leave the material where it is permanently. Here the Mishnah tells us that leaving it in place for as long as the tumah remains underneath is also considered leaving it there.
Understand the principle carefully. Ordinarily, a house that happens to be full is still a house: if the owner intends to clear out its contents, the fill is temporary and the structure retains its status as an ohel. But in every case of our Mishnah the owner plans to leave everything exactly as it is, and therefore there is no ohel. An ohel means a roof with space beneath it. Here there is no space beneath. The fill has become part of the building itself and it is staying. If a person builds a house, packs the entire interior solid and intends to keep it that way, it is not a house.
Consequently this structure has no din of an ohel, and we do not say that tumah spreads from one part of it to another. The Mishnah adds that this is true even where the tumah lies immediately alongside the keilim, right beside them but off to the side. In this sort of house the tumah is bokaas v'olah, it breaks through and rises straight upward all the way to the sky, and bokaas v'yoredes, it breaks through and descends straight down, but it does not travel sideways at all.
Why, then, should this building not qualify as an ohel? Or, following the Rambam's understanding, why should a substantial heap sitting out in the open not form one? Because the owner has made up his mind to leave the material where it lies, so the entire area is treated as genuinely packed. Nothing hollow is left. An ohel requires a covering with air beneath it, and here all there is is earth, or pebbles, or grain, none of which anyone plans to clear away. That is exactly why the tumah rises and sinks in a straight line and never shifts to either side.
The Bartenura's qualification
The Bartenura attaches an important condition. Everything stated here applies only when the spot where the tumah lies contains no cavity measuring a tefach in each of its three dimensions. Should such a cavity be present, we have moved into a different halachah altogether: that pocket of air constitutes an ohel in itself, and the tumah takes on the status of a kever sasum, a sealed grave, whose law is that whatever encircles it becomes tamei. Hence the ruling that tumah pierces straight upward and straight downward without spreading laterally is stated precisely for a case where the tumah's location holds no such cubic tefach of space.
Summary
To gather the halachah together: a house packed solid with earth or with pebbles whose owner announces that the fill stays; a house filled by a heap of grain that he has similarly resolved not to move; or, on the Rambam's understanding, a mound of pebbles or a heap of grain sitting outside any building. Even a pile on the order of galo shel Achan, which will stand only for as long as the tumah underneath it has not been cleared away, is enough to establish that no hollow remains, and where nothing is hollow there is no ohel. Accordingly, even when the tumah sits immediately adjacent to the keilim, as long as it is off to their side the keilim stay tahor, since the tumah pierces upward and downward and not sideways. The Bartenura supplies the exception: if the tumah's spot contains a cavity a tefach wide, a tefach long and a tefach high, that cavity is an ohel in its own right and the tumah becomes a kever sasum, making everything around it tamei. Without such a cavity, and where the owner means to let it all remain as it is for now, the tumah moves in one direction only, straight up and straight down.