Ohalos, Chapter 2, Mishnah 3. Tumas meis reaches a person along three separate avenues, and this mishnah is precisely about telling those avenues apart. Maga means physical contact with the tumah itself. Masa means bearing its weight, even where the person never touches it. Ohel means sharing a covering with it, the subject that the mishnayos ahead in this masechta will unfold in great detail. Earlier mishnayos have already taught that the various sources of tumas meis are not equal in strength, and here we are given five items that possess only the first two of these three powers. The mishnah introduces them: "eilu mitam'in bemaga uvemasa," these are the ones that convey tumah when touched and when carried, "ve'einan mitam'in be'ohel," while a person sharing a roof with them is unaffected.
The first item: etzem kisa'orah
"Etzem kisa'orah," a bone of a meis the size of a barley grain. Such a bone transmits tumah to one who touches it or carries it, but a person who is merely under the same roof with it remains tahor.
The Bartenura shows us where this distinction comes from in the pesukim. Concerning tumas ohel the Torah speaks of "etzem adam," the bone of a man, while concerning tumah through contact it writes simply "etzem," a bone. The extra word teaches that only a bone which is identifiable as coming from a human being spreads tumah through an ohel. For maga, however, no such recognition is required: a fragment as small as a se'orah suffices, and masa follows the same rule, since the tumah of carrying is derived from the tumah of touching. Tumas ohel it does not have.
The second item: eretz ha'amim
"Ve'eretz ha'amim," earth belonging to the territory of the nations, beyond the borders of the Land. A rabbinic decree imposed tumah on that soil, because a corpse could be buried at any spot there without anyone knowing of it.
The Bartenura clarifies that the mishnah has in mind a clod of that earth which someone brought with him across the border and into the Land. Because a barley-sized sliver of bone might be buried inside it, the clod is metamei bemaga uvemasa. It is not metamei be'ohel, however, since a bone of that tiny measure would not spread tumah through a covering even if it really were lying inside.
How do we know that the mishnah means earth brought into Eretz Yisroel, and not simply a person who traveled out of the Land? Because the decree of the chachomim extended even to the air of eretz ha'amim. One who steps outside of Eretz Yisroel becomes tamei immediately, without any touching or carrying, even while riding on a horse. Since our mishnah specifies maga and masa, it must be describing soil that was transported into Eretz Yisroel.
The third item: beis hapras
"Uveis hapras," ground that once held a grave and was afterward worked with a plow, so that the bones underneath were shattered and the pieces spread through the field. The term derives from perusah, something broken into pieces. The Bartenura cites the words of the novi in Yeshaya, "halo faros lero'eiv lachmecha," that you break off part of your loaf for a starving man who has nothing. Poros thus means to break a piece off, and this field earns its name because the plow reduced the bones there to broken fragments.
In truth, min haTorah such a field is not tamei at all, since the plow presumably reduced the bones to fragments smaller than a se'orah. The chachomim nevertheless decreed that it be metamei bemaga uvemasa, out of concern that perhaps one single fragment the size of a se'orah remained intact, and someone walking there might touch it or shift it from its place.
The fourth item: an eiver lacking basar karoi
"Eiver min hameis ve'eiver min hachai she'ein aleihen basar karoi": a limb severed from a meis, and likewise a limb severed from a living person, which does not have upon it basar karoi, sufficient flesh. As we have learned, this means the measure of flesh with which the limb could have healed had it remained attached to a living body. A limb lacking that amount does not have the status of etzem adam, and therefore does not convey tumah in an ohel; it is metamei only through maga and masa.
The fifth item: a shidrah or gulgoles that is incomplete
"Hashidrah vehagulgoles shechaseru," a backbone or a skull that is deficient. When intact, both of them are metamei be'ohel even with no flesh remaining on them whatsoever. But that strength attaches to them only in their complete state. As soon as a piece of either one is lacking, its din is like that of any ordinary bone: tumah through maga and masa, and no tumah through ohel.
The mishnah accordingly inquires, "kamah hu chesron bashidrah," what amount of loss disqualifies a backbone from counting as whole? "Beis Shammai omrim shtei chulyos," according to Beis Shammai a pair of vertebrae must be gone. "Uveis Hillel omrim afilu chulyah achas," Beis Hillel hold that the absence of one vertebra is enough.
"Uvagulgoles," and how much must be missing from the skull? "Beis Shammai omrim kimelei makdei'ach": a makdei'ach is a drill, so Beis Shammai measure the deficiency by the size of a hole bored by a drill. "Uveis Hillel omrim kedei sheyinatel min hachai veyamus": Beis Hillel measure by an estimation of a living person, for this skull too once belonged to a living man. If removing this amount from a living person would have caused his neshamah to depart, the skull is considered incomplete. That measure is smaller than the hole of a drill.
Drills, of course, are manufactured in a whole range of widths, as anyone who has bought one together with a set of bits is aware. The mishnah therefore clarifies, "be'eizeh makdei'ach amru," which drill was intended? "Bekatan shel rofim, divrei Reb Meir": in Reb Meir's view it is the small instrument physicians used. "Vachachamim omrim bagadol shel lishkah": the chachomim point to the large drill kept in the chamber of the Mikdash, and that is the more lenient of the two shiurim. Chazal sized the opening made by that larger drill as equal to a coin known as a pundyon.
Summary
Five sources of tumah convey tumah through maga and masa but not through ohel:
- A fragment of bone measuring a se'orah.
- A clod of eretz ha'amim carried in from beyond the border of the Land.
- A beis hapras, ground with a grave in it that was plowed over.
- A limb taken from a meis or from a living person, without basar karoi upon it.
- A backbone or skull that is deficient; while intact, each of them is metamei be'ohel too.
And regarding the amount that must be missing: for the spine, Beis Shammai require two vertebrae and Beis Hillel even one. For the skull, Beis Shammai measure by the hole of a drill, while Beis Hillel suffice with the smaller amount whose removal from a living man would have taken his life. According to Beis Shammai's drill measurement, Reb Meir speaks of the small drill of the doctors, and the chachomim of the large drill of the lishkah, which Chazal reckoned as the size of a pundyon.