THOUGHTS ON THE DAILY DAF
brought to you by Kollel Iyun Hadaf of Har Nof
Rosh Kollel: Rav Mordecai Kornfeld
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1) THE SIZE OF A "REVI'IS"
OPINIONS: The Gemara describes a Revi'is, which is a liquid volume measure,
in terms of cubic Etzba'os (thumb-breadths) -- which are measures of
distance. Rav Chisda says that a Revi'is (in liquid volume) is equal to the
volume held within a box which is 2 Etzba'os long, 2 Etzba'os wide, and 2.7
Etzba'os high (2 X 2 X 2.7 cubic Etzba'os, or 10.8 cubic Etzba'os). We are
also told that a Revi'is is equal to the size of 1.5 average eggs (Rashbam).
These correlations, which have ramifications for everything we do which
requires a Shi'ur of a Revi'is or Beitzah or k'Zayis (which is equal to half
of a Beitzah), have inspired much discussion among the Acharonim.
(a) The NODA B'YEHUDAH (d. 5553/1793), in the middle of the eighteenth
century, used his thumbs (Etzba'os) to determine the volume of an egg, using
the figure that Chazal gave for the size of an egg in terms of
fingerbreadths. Then, he took an egg and measured its actual volume. He
found that the actual volume of a Beitzah was only *half* of the figure that
he calculated using fingerbreadths! How could the Gemara equate these two
HALACHAH: The MISHNAH BERURAH (Bi'ur Halachah 271:13) writes that when
measuring for a Mitzvah d'Oraisa, such as for Kidush on the night of
Shabbos, one should be stringent and use the larger size of a Revi'is, the
size of at least two modern eggs. When measuring for a Mitzvah d'Rabanan,
one may rely on the smaller size of a Revi'is.
The Noda b'Yehudah (TZELACH, Pesachim 116b) concluded that either thumbs
have become larger than they were in the times of the Gemara, or eggs have
become smaller. It does not make sense that our thumbs are larger than those
of generations before us, he wrote, because we know that each generation is
weaker and punier than the previous one. Rather, he concludes, it must be
that eggs have become smaller.
Therefore, when it comes to any Mitzvah which involves the Shi'ur of a
Beitzah (or Revi'is), one should use *twice* the amount of what the Gemara
requires (for example, if the Gemara says that in order to fulfill the
Mitzvah of eating Matzah one must eat "one Beitzah," then nowadays one must
eat *two* Beitzim worth of Matzah, based on today's average egg size, in
order to compensate for the decrease in size of eggs).
This opinion is cited as the Halachah by the CHASAM SOFER (Teshuvos OC 127),
the VILNA GA'ON (Ma'aseh Rav #105), and the CHAZON ISH (Kuntrus ha'Shi'urim,
Chazon Ish OC 39).
The Chazon Ish translated the size of a Revi'is, as calculated by the Noda
b'Yehudah in terms of Etzba'os, into cubic centimeters. Using the figures of
the Noda b'Yehudah, who judged the value of an average thumbwidth to be 2.4
centimeters, the Chazon Ish arrived at a figure of 150cc (cubic centimeters,
or approx. 150 grams of water), as the size of a Revi'is.
However, the calculations of the Noda b'Yehudah and the Chazon Ish are faced
with serious problems, since they this size of a Revi'is seems to contradict
the rulings of the Rishonim.
1. The RAMBAM (Perush ha'Mishnayos, Eduyos 1:2) measured the size of a
Revi'is in dirhams (a common coin in Arabian countries in the time of the
Rambam, which is still used today in some places). The Rambam writes that a
Revi'is equals about 27 dirhams. Based on numismatic records and collectors'
dirhams, we know the approximate size of a dirham. 27 dirhams comes to about
*half* of the size of the Noda b'Yehudah's Revi'is!
(b) RAV CHAIM NA'EH (in Shi'urei Torah), who lived in Eretz Yisrael during
the time of the British Mandate, measured the Revi'is based on the dirham
which was in use in Israel during the Ottoman Empire (the Turkish
occupation), which was still in use during the times of the British Mandate.
During his time, the dirham weighed 3.2 grams, and therefore he concluded
that the Revi'is must be 86.4 grams, because according to the Rambam there
are 27 dirhams in a Revi'is (27 X 3.2 = 86.4) (he points out that this also
happens to be the Gematria of "Kos" (86)). The width of a Etzba then,
working backwards, would be 2 centimeters, which is closer to the average
2. Second, the Rambam (Hilchos Eruvin 1:12) measured the weight of a Revi'is
based on the weight of the Dinar, a common coin used in the times of the
Gemara, and says that a Revi'is equals 17.5 Dinars. We know the weight of
the Dinar to which the Rambam is referring since he based his measurements
on the BEHAG and the RIF (Kidushin 12a) who write that the Dinar in the
times of Chazal was equivalent to the contemporary Arabic "Sheshdang" Dinar.
Furthermore, the Rambam himself spells out the weight of a Dinar in terms of
barley grains, which later Rishonim correlate to carob pits (four barley
grains are equal to one carob pit). These modes of measurement correlate
nicely even today, and thus the weight of the Dinar is fairly well known (i.e. it is highly unlikely that both the barley grains and the carob pits
shrank equally since the days of the Rishonim). The size of a Revi'is as
calculated based on the weight of the Dinar comes out -- again -- to *half*
the size of the Revi'is as measured by the Noda b'Yehudah!
3. The Mishnah says in Kelim (17:11) that the measures of volume which were
used by Chazal were the same as the Italian (Roman) measures. Based on
comparisons to old Roman measures, it can be demonstrated that the size of a
Revi'is was much smaller than the size proposed by the Noda b'Yehudah (see
Midos u'Mishkalos Shel Torah, 1:48).
4. The MISHNAH BERURAH (OC 271:13, Bi'ur Halachah) points out that the
Gemara in Yoma (80a) says that a person can hold more than a Revi'is (which
is 1.5 eggs) in both of his cheeks at one time. The Mishnah Berurah says
that the average person can hold the volume of at most about two modern eggs
at one time in his cheeks. However, according to the Noda b'Yehudah, who
says that a Revi'is contains twice the amount of eggs than it did in the
time of the Gemara, a person should be able to hold at least *three* modern
eggs in his mouth at once -- but we do not find anyone with cheeks that
5. The CHAZON ISH (recorded in the Steipler Ga'on's SHI'URIM SHEL TORAH 3:9-
10) himself asks another question on the measurement of the Noda b'Yehudah.
Throughout the generations, the Jewish people have had the custom to use
between 70 and 100 grams of silver for the Mitzvah of Pidyon ha'Ben,
redeeming the firstborn son. The Rambam writes that a Revi'is is 17.5 Dinars
(see above, (2)), while we know that Pidyon ha'Ben is done with 20 Dinars.
If so, the weight of the silver used for Pidyon ha'Ben should be fourteen
percent more than the weight of silver which is equivalent to a Revi'is.
However, if a Revi'is is 150 grams (according to the calculations of the
Chazon Ish, based on the Noda b'Yehudah), then one should use fourteen
percent more of that weight in silver for Pidyon ha'Ben -- or about 170
grams of silver, and that was never the custom anywhere!
6. Interestingly, some ancient eggs actually survived to our times. I heard
from Harav Yakov Gershon Weiss (author of Midos u'Mishkalos Shel Torah) that
mummified eggs found in the pyramids, as well as eggs preserved by the ashes
of Vesuvius in the ruins of Pompei, are more or less equal in size to
(The "TESHUVAH ME'AHAVAH," a student of Noda b'Yehudah's, rejected his
Rebbi's calculations based on the fact that "the Noda b'Yehudah was one of
the tallest men in the generation, and he measured with his own thumbs!" The
Chasam Sofer, however, rejects this argument, pointing out that although
2.4cm is a bit on the large side, it is not uncommon for thumbs to be that
size -- see Midos u'Mishkalos Shel Torah ch. 87.)
However, this size of the Revi'is is also problematic:
1. The weight of old dirhams, which are very common, vary between 2.7 and 3
grams. If so, the maximum size of a Revi'is should be 81 grams, and not 86
as Rav Chaim Na'eh states, who measured the Revi'is based on a dirham of 3.2
(c) The third opinion gives an even smaller calculation of the size of a
Revi'is than the one given by Rav Chaim Na'eh, or approximately 74 cc. This
opinion bases the size of the Revi'is on the size of the dirham at the time
of the Rambam. Historical records show that the dirham has increased in
weight through the centuries, and Rav Chaim Na'eh's dirham was larger than
the Rambam's. (See MIDOS U'MISHKELOS SHEL TORAH ch. 60-64).
2. Second, our records of the "Sheshdang" Dinar also show that the Dinar is
4.25 grams, making a Revi'is (which is 17.5 Dinars) about 74.4 grams. When
divided by 27, that figures gives the weight of a dirham as being 2.75
grams, which fits within the range of the average weight of old dirhams.
3. Third, according to Rav Chaim Na'eh who says that a Revi'is is 86 grams,
an egg today should have an average size of 57 1/3 grams. (Since an egg is
2/3rds of a Revi'is, an egg should be 2/3rds of 86, which is 57 1/3.) In
reality, the egg is somewhat smaller than that. According to the calculation
of the Revi'is based on the old dirhams as we mentioned above, the average
egg should be about 50 grams, which is much closer to the actual size of our
4. Fourth, the size of an Amah is the distance from the elbow until the tip
of the middle finger of the average arm. If the average Etzba is 2
centimeters, as Rav Chaim Na'eh asserts, and we know that there are 24
Etzba'os in an Amah, then the Amah should be 48 centimeters. The length of
the average arm, from elbow to tip of middle finger, though, is smaller than
that. Using the measure of the Etzba based on the Revi'is as calculated by
using dirhams, the Amah comes out to 46 centimeters, which is closer to the
length of the average arm.
5. RAV SHLOMO ZALMAN AUERBACH zt'l points out that the Gemara in Shabbos
(14a) says that the Rabanan made a Gezeirah that a person who drinks liquids
which are Tamei becomes Tamei. Chazal enacted that Gezeirah so that a person
would not eat Terumah at the same time that there is a Revi'is of Tamei
liquid in his mouth (see Tosfos in Shabbos). Rav Shlomo Zalman Auerbach says
that according to the size of a Revi'is as calculated by Rav Chaim Na'eh,
one cannot possibly fit any food into one's mouth when there is already a
This fits well with the weight of the Dinar and with the size of common
eggs. The only remaining problem is the size of fingerbreadths. For a
Revi'is of 74 cc, one would expect that the average thumbwidth is 1.9cm,
while a width of over 2cm is much more common. It might be either that they
indeed had smaller fingers in the earlier generations, or that they measured
fingerbreadths by pressing their fingers closer and harder together.
What is the larger Shi'ur with which a person should be stringent? The
CHAZON ISH writes that it is 150 cc. The IGROS MOSHE (OC I:36) says that it
is enough to use approximately 120 cc, based on the average fingerbreadth
being 2.25 centimeters. The EINAYIM LA'MISHPAT (Berachos 39a) writes that
the Vilna Ga'on gave a Kidush cup to his Talmid, Rav Yisrael mi'Shklov,
which was measured to be approximately 120 cc.
B'Di'eved, one should try to have a cup which holds at least 100 cc (which
is the volume of two eggs), as the Bi'ur Halachah writes, and for Mitzvos
d'Rabanan a person may rely on Rav Chaim Na'eh's Shi'ur of 86 cc, or in
extenuating circumstances, 74 cc, as described above.
2) "ZUGOS" AND "SHEIDIM"
The Gemara discusses at length the concern of performing certain actions in
pairs (such as eating or drinking a multiple of two of any item), and how
doing so gives certain power to the Sheidim to do harm. What is the
understanding behind the Gemara's concern for Zugos, and do the Gemara's
statements apply to us, nowadays?
[I] WHY "ZUGOS?"
The Acharonim propose different rationalizations for the phenomenon of
"Zugos," or pairs?
[II] "ZUGOS" TODAY
(a) The SEFER MALKIEL teaches that the existence of Sheidim represents the
forces of nature through which Hashem punishes those who demonstrate a lack
of faith in Hashem. The primary description of Hashem that we know is that
Hashem is One. He is the ultimate and only One, the pure Singularity in the
world. When a person performs an act of Zugos, or "multiplicity," he gives
the Sheidim a foothold by demonstrating a lack of Oneness in the world. When
a person eats an odd number, such as three, then the even numbers pair and
cancel each other out leaving a singular "one," and that is why the Sheidim
have no power over odd numbers.
(b) The MAHARAL (Gevuros Hashem, ch. 38; Be'er ha'Golah, Be'er ha'Sheni, p.
28; Nesivos Olam, end of Nesiv ha'Avodah) adds a reason to explain *why* the
Sheidim dominate wherever there is a lack of Yichud Hashem.
The Maharal explains that the Sheidim are a secondary consequence of the
Creation of the world. That is, when Hashem created the world, a secondary
outgrowth was the development of Sheidim. That is, they were not meant to be
the purpose of Creation, like the other creatures of the world. Rather, they
are a consequence of Creation, and they came into being since the world
would not be complete without them. Since their whole existence is
secondary, i.e. with a less direct connection to Hashem, they have power
over anything that is secondary, i.e. which is less directly connected to
(c) Following the path of the Rambam, who, in Moreh Nevuchim, rationalizes
most Mitzvos that seemingly lack purpose by connecting them to the practice
of early idolators, the following may be suggested. One of the basic tenets
of the belief of the polytheists, who believed that there were many gods,
was that all of the gods stemmed from two basic forces, one of good and one
of bad (Sanhedrin 39a). Therefore, they had a practice to make sure to eat
two of everything to satisfy the forces of both good and evil. For this
reason, the Rabanan decreed that the Jews should be careful not to eat two
of everything, and certainly not to do so intentionally, for doing so
demonstrates a trace of idolatry for which a person will be punished. (M.
What is the Halachah? Do the stringencies of Zugos apply today?
QUESTION: We might ask, how could the Rabanan make an enactment to eat
Lechem Mishnah -- two loaves -- on Shabbos? That should be a problem of
Zugos just like drinking the Arba Kosos!
(a) The RASHBAM (110a, DH Rabah) writes that as time went on, the concern
for Zugos decreased more and more. (According to the third explanation above
this is very logical, because no one remembers nowadays how the idolaters
used to conduct themselves.) We find that even in the times of the Amora'im,
the concern for Zugos was decreasing, as the Rashbam explains.
TOSFOS (Yoma 77b and Chulin 107b) explains that nowadays (that is, during
the times of Tosfos), we no longer show any concern for Zugos at all.
Apparently, he explains, the forces that had power over Zugos have become so
diminished that they are extremely rare and do not warrant any concern.
However, the TUR (OC 170) briefly writes that one should not eat or drink
anything in pairs. He also mentions (OC 183) that a person should not recite
Birkas ha'Mazon after drinking two cups of wine during the meal, because he
will be so worried about Sheidim harming him that he will not be able to
concentrate on the blessings. The BEIS YOSEF there writes that the Tur
should have omitted this Halachah, because Tosfos writes that the Sheidim
are no longer prevalent, and in the SHULCHAN ARUCH he indeed leaves them
out. The Acharonim suggest various answers as to why the Tur mentions Zugos
Perhaps the TUR mentions the Halachah of Zugos with regard to Birkas
ha'Mazon because in the case of Birkas ha'Mazon, it is a matter of one's
ability to concentrate on the blessings. A person might not be able to
concentrate if he drank two cups during the meal, because he is so worried
about being harmed by Sheidim. Even though, in reality, there is no longer
any concern for Sheidim, some people are still worried about them, and such
a person's mind will not be clear and calm enough to concentrate when he
recites Birkas ha'Mazon. Therefore, the Tur says that he should not recite
Birkas ha'Mazon after drinking two cups.
Why, though, does the Tur mention that a person should avoid eating or
drinking in pairs? It could be that even though right now the Sheidim are no
longer prevalent, and in everday practice we do not have to be concerned
with eating Zugos, nevertheless, the Tur means to caution that we should
never enact a decree or create a custom that involves eating or doing
something in pairs. The reason for this is twofold. First of all, perhaps
the Sheidim will return. Furthermore, the Gemara (110b) says that even when
the Sheidim have no power, "Kishuf," witchcraft, still has power over Zugos.
That is, if a sorceror sees someone eating Zugos, he can harm him more
easily. Although, we are normally not concerned with the possibility of
"Kishuf," since it is rather rare to meet up with a sorceror, nevertheless,
a decree or custom that will put a person in danger of Kishuf should be
(a) When it comes to the Arba Kosos, the Rabanan decreed that one must drink
the entire cup (and by drinking a majority of the cup, one is considered as
if he had consumed the entire cup). In contrast, when it comes to Lechem
Mishnah, there is no requirement to eat two *entire* loaves of bread. Just
reciting ha'Motzi over Lechem Mishnah is not considered Zugos. (Y. Shaw)
(b) Our Gemara (110b) says that loaves of bread does not have a problem of
Zugos because they are "completed in the hands of man." (However, some old
texts of the Gemara, as well as that of Rabeinu Chananel, do not have the
Girsa there of "Kikaros.")
(c) The MAHARSHAM cites the Zohar (Parshas Ekev, p. 273a) that asks this
question and answers that Sheidim do not have dominion on Shabbos (although
they apparently *do* have dominion on Yom Tov, as we see from the Gemara's
question concerning the Arba Kosos).
RAV YAKOV EMDEN asks that our Gemara (112b) concludes that the Sheidim are
*more* prevalent on Friday night than during the week! In fact, this is why
we do not recite the verses normally recited before Shemoneh Esreh (in Chutz
l'Aretz) on Friday night; so that we will finish Ma'ariv late and have to
return home after dark, and after the lamps have gone out (TUR OC 267,
citing the Ge'onim).
How is this to be reconciled with the Zohar, which says that the Sheidim
have no power on Shabbos? Furthermore,
He answers that the Zohar itself asks this question (Vayakhel 205a). The
Zohar answers that the Rabim (public) have nothing to fear on Shabbos.
Individuals, though, could be affected by the forces of the Sheidim on
Shabbos. Since Lechem Mishnah was enacted for everyone, there is no concern
for Sheidim. An individual, though, should not go out alone on Friday night,
out of concern for the Sheidim that dominate then.