Nazir chapter 9, mishnah 3. This mishnah is brought here even though it has no direct connection to the laws of nezirus, because the previous mishnah closed with the concept of 'raglayim ladavar' - that when there is substance to the matter and a presumption of tumah exists, we maintain that tumah. Here too we will deal with the presumption that a place is a cemetery: when do we assume that the continuation of the area is also a burial site.
"HaMotzei Mes Batchilah" - One Who Finds a Corpse at the Outset:
A person who finds a corpse buried "mushkav k'darko" - lying in the normal fashion, the way a Jew is buried. The wording "batchilah" comes to tell us that this corpse was not found after other bodies had already been discovered; rather, it is a single, isolated body. In such a case: "notlo v'es tefisaso" - he removes the corpse together with the moist earth beneath it, which presumably contains body fluids, and buries it elsewhere.
The reason for this: when several bodies are found, and it appears that the place was part of an official burial ground, they may not be moved from their place. But when a single person is buried there, it stands to reason that this was a temporary burial, and therefore he may be transferred from there. The corpse does not acquire its place, it has no rights to that ground, and we do not assume that this is a designated burial site.
"Matza Shnayim" - He Found Two:
With two corpses as well the law is the same: "notlan v'es tefisasan" - he removes the bodies along with the moist earth beneath them.
He Found Three Corpses:
Here it depends on the distance between the bodies, in the language of the mishnah: "yesh bein zeh lazeh me'arba amos v'ad shemoneh - harei zu shechunas kevaros" - if there is between one and the next from four amos up to eight, this is a burial site. Three distinctions emerge:
Less than four amos: the unusual closeness indicates that the bodies were buried there temporarily and under duress, and this is not an official burial ground.
From four amos up to eight: this is a 'shechunas kevaros', an official burial site, and therefore the bodies must be left in their place.
More than eight amos: once again we view them as isolated graves and not as an official burial ground.
The basis of these measurements: burial caves were generally made in the dimensions of four amos by six amos, and their diagonal is eight amos. Therefore a distance of between four and eight amos indicates that the bodies are part of that same cave.
The Examination of Twenty Amos:
Once three bodies have been found buried together, there is an obligation to examine the ground from that point onward for twenty amos. This measurement stems from the way the caves were built:
One burial cave measuring four amos by six amos.
A courtyard situated between the caves, measuring six amos by six amos.
An additional burial cave on the other side of the courtyard.
The length of the two caves together with the courtyard between them is eighteen amos, and since the examination is sometimes made along the diagonal, the diagonal adds two amos, making twenty amos in all.
He Found a Corpse at the End of the Twenty Amos:
If within those twenty amos, and even at their very end, another corpse is found, one must examine an additional twenty amos. For as far as we know this is not the end of the burial site, and it is possible that this is the beginning of another burial site. The reason for this assumption, as the mishnah sums up: since it has been revealed that the area was designated for graves, we must assume, or at least suspect, that even this single body is part of a system of graves.
By contrast, a single corpse found at the outset is removed along with its tefisah, and there is no need to assume that there are additional bodies in the vicinity. But once this corpse is found in the continuation of an existing site in which three bodies were found together, even if it is found at the end of the twenty amos, we must assume that we are dealing with an official burial ground and not with an isolated body.
In summary: in this mishnah we learned the parameters of the presumption of a cemetery: one corpse or two - he removes them along with the earth beneath them, since they are no proof of a designated burial site; three corpses at a distance of between four and eight amos from one another - this is a shechunas kevaros, and they may not be moved from their place, and one must examine twenty amos onward, the measure of two caves and the courtyard between them with the addition of the diagonal; and if a corpse is found at the end of those twenty amos, one examines another twenty amos, for once the area has been established as a burial ground, even a single corpse is considered part of the system of graves.