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Week 12 - Monday - 14 Feb. 2000

ERUVIN: CHAPTER 1: MISHNA 5

If it is made of straw or reeds, it is considered as if it were of metal; if bent it is considered as if it were straight; if round it is considered as if it were square. Whatever has a circumference of three tefahs, has a width of a tefah.

Kehati

This mishnah is the continuation of Rabbi Yehudah's statement in the preceding mishnah: "Wide, even though it is not strong."

If it - the beam, is made of straw or reeds - which cannot bear an ariah, it is considered as if it were of metal - which can bear an ariah; if - the beam is - bent - and an ariah cannot rest on it, it is considered as if it were straight - and therefore fit; if the beam is - round - and an ariah cannot rest on it, it is considerd as if it were square. And what is the measure of the round beam that makes the mavoy fit?

Whatever has a circumference of three tefahs - has a width of a tefah - hence we know that a round beam with a circumference of three tefahs is fit. The Gemara learns this from the verse, "And he made the molten sea of ten amah from brim to brim, round in compass, and the height thereof was Five amah; and a line of thirty amah did compass it round about" (I K. 7:23). I.e., the sea was round, and its diameter, from one edge to the other, was ten amot, and its circumference was thirty amot. This measure is not precise, but only stated in round numbers. Rambam similarly writes that, according to the rules of geometry, any round object with a diagonal line (i.e., diameter) of one amah has a circumference of c. 3 1/7 amot. Since this is an irrational number, the Sages used the whole number. Geometry does indeed agree with Rambam: if the diameter is one amah, the circumference (rounded off to two decimal points), is 3.14 amot. This number (3.14...) is known as pi.

According to Rabbi Yonatan of Lunel (following one opinion in the Jerusalem Talmud), this mishnah records Rabbi Yehudah's opinion, from which the Sages differ. According to other commentators

(following another opinion in the Jerusalem Talmud), only the first section of the mishnah follows Rabbi Yehudah's opinion. Regarding, however, the bent or round beam, even the Sages agree that it is

considered as if it were straight or square. If, however, the curve of the bent beam is outside the mavoy, so that if the bent part were removed there would be a space of three tefahs between the sections of the beam, the beam is invalid, according to the Sages (Jer. Talmud, Rambam, Rabbeina Asher).

ERUVIN: CHAPTER 1: MISHNA 6

The two lehis of which they spoke, their height is ten tefahs, and their width and their thickness is any measure. Rabbi Yose says: "Their width is three tefahs."

Kehati

After the dimensions of the beam were taught, this mishnah teaches the dimensions - height, width, and thickness - of the lehi.

The two lehis of which they spoke - regarding which the Sages and Rabbi Eliezer disagree (mishnah 2, above), the latter requiring two lehis, one on either side of the entrance to the mavoy, while the Sages require only one lehi on one side,

their height is ten tefahs - i.e., even according to Rabbi Eliezer, who requires two lehis, their minimum height must be ten tefahs as the height of the mavoy.

However, even if the mavoy is higher than ten tefahs, a lehi ten tefahs high suffices to make it fit (Rambarn, Bartenura),

and their width and their thickness - of the lehis, is any measure - the Gemara states: "How much is 'any measure'?" Even as a thread of a sarbel (a type of thick garment that was worn during the period of the Tannaim and the Amoraim). According to another view, the "thread of a sarbel" is of the thickness of a finger (Mordekhai, in the name of Maharam). According to yet another interpretation, this measure is even less than the width of a finger, i.e., any thickness (Bet Yosef, Magen Avraham).

Rabbi Yose says: Their width is three tefahs - since the lehi represents a partition, it must be something substantial, and is therefore valid only if it is at least three tefahs wide (Rabbi Yonatan of Lunel, Bartenura). The halakhah does not follow Rabbi Yose.

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