In this lesson we turn to Mishnah 7 of the first chapter of Maseches Eduyos. From here on the Mishnah moves to a new type of subject matter, and the topics have no substantive connection to one another. What unites them is the phenomenon the Mishnah is seeking to collect: a dispute in which Shammai himself disagrees with Beis Shammai. Each mishnah has a world of content all its own, and the subject of Mishnah 7 is the transmission of tumah by way of ohel (a covering, or tent).
Background: Tumas Ohel
The sources of tumah are many and varied - thirteen of them are listed in the Torah - and they transmit tumah in a number of different ways, seven in all. But transmission by way of ohel is entirely unique to the ultimate source of tumah, the body of a dead person. A corpse conveys tumah not only through direct contact or by having its weight carried (contact and carrying), but even through an ohel.
The ohel comes in three forms:
A person is under one roof together with the source of tumah.
A person is directly above the tumah.
A person is directly beneath the tumah.
The Measures of Tumah
A complete body - conveys tumah through an ohel, and so too does flesh from a corpse in the amount of a kezayis (the volume of an olive).
A bone with no flesh on it - a bone the size of a barleycorn is enough, that is, a fragment of bone the size of a grain of barley, to convey tumah through contact and through carrying.
But in order to convey tumah through an ohel, meaning that a person under one roof with the bone fragments becomes tamei, a larger quantity of bones is required. How much bone is needed for this? That is the dispute before us.
The Dispute in the Mishnah
"Beis Shammai omrim: rova atzamos min ha'atzamim, bein mishnayim bein mishloshah" - human bones convey tumah through an ohel once they reach the volume of a rova hakav, that is, a quarter of a kav, roughly five hundred cubic centimeters of bone fragments. And it makes no difference whether they came from one body or from several bodies, even from two or three. Once this quantity has been gathered together, anyone under one roof with it becomes tamei, and so do his belongings.
"Beis Hillel omrim: rova atzamos min hagviyah, meirov habinyan o meirov haminyan" - there are two limitations here. First, the bones must come from a single corpse, that is, from the skeleton of one individual. Second, they must constitute rov habinyan - the majority of the skeletal structure, or rov haminyan - the majority of the bones in terms of number.
"Shammai omer: afilu me'etzem echad" - Shammai himself disagrees with Beis Shammai and holds that no multiplicity of bones is needed at all. If a single bone, such as the thigh bone, contains the volume of a rova hakav, it conveys tumah through an ohel.
The Bartenura's Explanation of 'Rov Binyan' and 'Rov Minyan'
The Bartenura explains that 'binyan' refers to the skeletal structure, and that the issue there is essentially one of volume - that is rov binyan. 'Rov minyan' means the majority of the number of bones: according to the count of Chazal there are two hundred and forty eight bones in the body, and the majority of them comes to one hundred and twenty five. (It is difficult to reconcile this count with the figure accepted today for an adult, about two hundred and six bones, although in children the bones are indeed more numerous.)
It emerges, according to this approach, that Beis Hillel require the bones to come from a single skeleton and to make up either rov binyan (the majority of the body's structure) or rov minyan (the majority of its count) - at least one hundred and twenty-five bones - in order to convey tumah in an ohel. This of course applies even to a very small skeleton, such as that of an infant. Beis Shammai hold that it is enough for the bones to combine even from several skeletons, while Shammai is satisfied with a single bone that contains the required measure.
The halachah:
If we follow the ruling of the Rambam, it does not match any one of these opinions exactly. The Rambam rules that a significant portion of the skeleton is required, but this can come about in several ways:
A complete skull, that is, the cranium.
A complete spine, the vertebral column, with its eighteen vertebrae.
Rov binyan, the majority of a person's structure - according to the Rambam, the majority of the leg bones, the spine and the ribs.
Rov minyan - one hundred and twenty-five bones of any size whatsoever.
A mere collection of bones, provided that they come from a single body and together amount to a total volume of a quarter-kav.
In summary: In this Mishnah we dealt with the measure of bones that conveys tumah in an ohel: Beis Shammai are satisfied with a quarter-kav even from several bodies, Beis Hillel require a quarter-kav from a single corpse and in a form that constitutes rov binyan or rov minyan, and Shammai deems even a single bone containing that measure sufficient. As for the halachah, the Rambam took a middle path and listed several ways in which bones convey tumah in an ohel.