Ohalos, Chapter 18, Mishnah 7. Our mishnah contains two separate subjects. It opens with a case of someone who buys a field just over the northern border of Eretz Yisrael, in the region the Mishnah calls Suria, and it closes by introducing a fresh topic that will occupy the rest of the tractate: the tumah that Chazal placed upon the dwelling places of non-Jews.
What is Suria?
Suria corresponds roughly to present day Syria. On a map of Eretz Yisrael it sits at the upper right, to the northeast. This is the area of Aram Naharayim and Aram Tzovah, the lands conquered by Dovid Hamelech. His conquest there, however, carries a special status: it is classified as a kibbush yachid, an individual conquest, because Klal Yisrael as a whole was not there together with him. A conquest of that sort does not truly absorb the territory into Eretz Yisrael. Others explain the limitation differently: Dovid went out to capture Suria before he had completed the conquest of Eretz Yisrael proper, so that portions of land which the Torah itself calls Eretz Yisrael were still outside his control when he took Suria.
So where does Suria stand in halacha? The Tanna'im disagree, and their dispute surfaces in Meseches Gittin, in Meseches Avodah Zarah and in other places as well: should this territory be governed by the halachos that apply within Eretz Yisrael, or should it not? The practical upshot pulls in both directions. Certain areas of halacha treat Suria as though it were part of the Land, and other areas do not. As far as our topic goes, the tumah of eretz ha'amim, Suria is no better than any other territory beyond the borders: it is tamei just as they are. Yet when it comes to agricultural obligations the picture reverses. Vegetables grown in a garden in Lakewood, in Boro Park or in Flatbush are free of terumos and maasros altogether, whereas whatever grows in the soil of Suria must be tithed.
Two components of tumas eretz ha'amim
Tumas eretz ha'amim, the tumah Chazal decreed upon the lands of the nations, actually breaks into two separate elements. There is a tumah of the gush, the earth itself, contracted by contact with the ground, and there is a tumah of the avir, the airspace, contracted merely by being there even without touching the soil. Suria received only the first of these. There is tumah of the gush in Suria, but there is no tumah of its airspace.
The case of the mishnah
Now to the case itself. The Tanna speaks of "HaKoneh sadeh b'Suria", a man who acquires a field in that region, and adds that it is "smuchah l'Eretz Yisrael", sitting flush against the border of the Land. The condition is "im yachol lehikanes lah b'taharah": is he able to get into that field while remaining tahor, meaning that he can arrive there without setting foot on any ground that has the status of eretz ha'amim? If so, the Mishnah rules "tehorah": his field is tahor. Picture a man lucky enough to have acquired his plot exactly on the borderline, so that from where he is standing inside Eretz Yisrael he takes one step forward and he is already in his own field, with no eretz ha'amim traversed on the way. Such a man does not become tamei.
Here a reader should raise his hand and ask a question. If Chazal decreed tumah upon the gush, the very ground of Suria, of what help is it that my field abuts the border? Granted that I need not walk across anyone else's field along the way, but my field itself is located in Suria, and Chazal placed tumah on the soil of eretz ha'amim. The moment I set foot in it, should I not become tamei?
The answer, as the Bartenura explains, is that precisely in this situation Chazal never extended the gezeirah. The field belongs to a Yisroel, and it can be reached without passing through any eretz ha'amim; under those two conditions the decree of tumah on the earth was never applied.
The mishnah continues that this field is nonetheless "chayeves b'maasros u'vashvi'is", obligated in maasros and in the laws of the seventh year, and this is true of all of Suria. Shmitah too applies in that land; the only question is whether the obligation there is min haTorah or mid'rabbanan, and in that there is a machlokes.
A second approach
A very different reading of the Mishnah exists as well, and this is how some learn the Rambam. On this reading, owning the field earns a person no leniency whatsoever. Practically speaking, the soil of Suria transmits tumah to anyone who treads on it, and it makes no difference whose name is on the deed, since the gezeirah of Chazal fell on the gush there. If so, what is the Mishnah coming to tell us? Something quite different. Since the airspace of Suria was never declared tamei, a man whose plot lies immediately alongside the border of the Land has a workable option available to him: let him ride in mounted on an animal, or have himself carried in inside a container of some kind. So long as his feet never make contact with the earth, he stays tahor, for the avir there transmits nothing.
Observe how much rides on the absence of anything in the intervening stretch. Should there be a patch of genuine eretz ha'amim in between, or a beis hakevaros, or a beis hapras, he would pick up tumah through the airspace itself, feet off the ground or not. Only because no such thing stands between the Land and his plot does riding or being carried accomplish anything for him. And the first approach shares this element too: part of what makes the field tahor is that neither a beis hakevaros nor a beis hapras is situated along the route from Eretz Yisrael to it.
On either reading of the Mishnah, one conclusion is beyond argument. A man who buys ground in Suria has not thereby freed himself from tithing. Terumos and maasros must be separated from his crop, and the fact that some authorities hold this obligation to be only mid'rabbanan does not remove it.
Medoros ha'akum
From here the mishnah opens an entirely new sugya, one that will carry us through the remainder of the tractate. "Medoros ha'akum tmei'im", the dwellings of non-Jews are tamei. The word medoros comes from dirah, a residence. We are speaking of such homes within Eretz Yisrael. The reason for the tumah is that they would bury nefalim in their houses, a nefel being an infant that emerged before its time. This tumah is a decree of Chazal.
The mishnah asks: "Kamah yeishev b'sochan v'yitzarech bedikah?" How long must the non-Jew have lived there for the house to require a bedikah, an examination, before a Yisroel may dwell in it in taharah? The answer: "Arba'im yom", forty days. Only if he resided there at least forty days does the concern arise.
Why forty days? The whole apprehension revolves around buried nefalim, infants that never came to a live birth. A miscarriage that occurs before the fetus has completed forty days from conception produces no tumah at all; it is only from the fortieth day and on that such a fetus is metamei. It follows that a non-Jew who occupied the house for forty days or less leaves nothing behind to be suspicious about. At this point the sharp listener protests: how do we know the woman had not conceived well before the family ever entered the house? The poskim take up that difficulty, but these are the boundaries within which Chazal set this tumah. Once forty days of residence have passed, a chshash of tumah exists, and the house automatically bears the status of tamei until a bedikah is carried out; what that bedikah consists of, and which spots in the house must be checked, we will learn further on.
The Tanna now adds a chiddush with the words "she'ein imo ishah", prefaced by af al pi: the ruling holds good even for a man who lived there alone, with no wife in the house. One explanation given is that they are not careful in matters of arayos. The poskim suggest a second reason: Chazal had no wish to open up distinctions between a residence where there was a wife and a residence where there was not. Either way the halacha does not budge. Forty days of occupancy by a non-Jew mean that the place must be treated as tamei until it has been checked.
The Mishnah's final clause offers an exemption. "V'im haya eved", if there was an eved Ivri, "o ishah", or a Jewish woman, and their role was "m'shamrim oso", standing guard over the place to see that nothing of the sort was buried in it, then "eino tzarich bedikah": no examination is called for. The Rishonim point out that such a guardian was not required to be on the premises around the clock. It suffices that the non-Jew was aware they might come through the door at any moment.
A striking halacha
One observation deserves a place at the end. This gezeirah of Chazal was enacted for the Land alone; beyond its borders it was never instituted. Neither the tumah of medoros ha'akum nor that of a beis hapras has any force in chutz la'aretz. The result is something of an irony: a kohen abroad may walk into the home of a non-Jew, while in Eretz Yisrael he may not. What accounts for that? One explanation is that outside the Land he is exposed to tumas eretz ha'amim regardless, so this decree would have added nothing. Inside Eretz Yisrael, where the standard of taharah is on an altogether higher plane, Chazal found it fitting to impose this tumah.