THOUGHTS ON THE DAILY DAF
brought to you by Kollel Iyun Hadaf of Har Nof
Rosh Kollel: Rav Mordecai Kornfeld
Ask A Question about the Daf
SUKAH 17 - Dedicated by Seth and Sheila Jutan of Atlanta, Georgia, in memory
of her grandfather, Mr. Bernie Slotin (Dov Ber ben Moshe Mordechai z'l), who
passed away on Chol ha'Moed Pesach (18 Nisan 5759 - April 4, 1999).
1) HALACHAH: FOUR "TEFACHIM" OF INVALID "SECHACH"
 FOUR TEFACHIM OR FOUR AMOS?
HALACHAH: The Amora'im argue as to the width of the strip of invalid
Sechach that can invalidate a Sukah (if it divides the Sukah into sections
that lack 7 by 7 Tefachim or three walls). How do we rule Halachically in
this matter? Will a four-Tefach strip invalidate the Sukah, or must it be
four Amos wide to invalidate the Sukah?
 LESS THAN FOUR TEFACHIM
(a) The HILCHOS GEDOLOS rules leniently, that it must be four Amos wide to
invalidate the Sukah. The ITUR (cited by the ROSH 1:32) explains that the
Yerushalmi supports this ruling. Our Sugya also provides support for this
ruling, he continues, since according to the Talmidim of Naharda'a Rav and
Shmuel argued this point, and the Halachah always follows Rav (who say four
Amos, according to the Talmidim of Naharda'a) as opposed to Shmuel, with
regard to Isurei Torah.
(b) However the RIF and RAMBAM and other Poskim rule like Shmuel, that even
four Tefachim of invalid Sechach can invalidate the Sukah. The RAMBAN (cited
by the Rosh, ibid.) explains that every mention of "Dofen Akumah" in the
Shas supports this view, since according to those who say four Amos are
needed even in middle of the Sukah, there is no difference between Sechach
Pasul next to the wall, and Sechach Pasul in middle of the Sukah; there is
no such thing as Dofen Akumah! This is indeed the ruling of the SHULCHAN
What about less than four Tefachim of invalid Sechach? It is clear that it
will not invalidate the Sukah, but is it considered like valid Sechach? May
a person sleep and eat under it, or must he make sure to sit under the valid
part of the Sechach?
(a) RASHI on Daf 18a (DH she'Ein) writes, without citing proof, that one may
even sit under the Sechach Pasul if it is less than 4 Tefachim wide.
HALACHAH: Although the SHULCHAN ARUCH (632:1) only brings Rashi's opinion,
the MISHNEH BERURAH (3) cites the Ra'avad and rules that it is better to
avoid eating under Sechach Pasul that is three to four Tefachim wide.
(b) The RA'AVAD (on the Rif, to Daf 14a), though, takes issue with this
ruling and explains that one may not eat under the invalid part of the
Sechach if it is larger than three Tefachim wide.
2) THE AMOUNT OF "SECHACH PASUL" THAT WILL INVALIDATE A SMALL SUKAH
QUESTION: The Gemara teaches that in a small Sukah of 7 by 7 Tefachim, even
3 Tefachim of Sechach Pasul will invalidate the Sukah. Rashi explains that
since 3 Tefachim is too large to apply the principle of Lavud, that part of
the Sechach is considered to be separate from the rest of the Sukah and
cannot join to add up to the required Shi'ur of 7 Tefachim in order to make
the Sukah valid. It is clear, though, that less than 3 Tefachim of Sechach
Pasul is valid for a small Sukah.
Why is less than 3 Tefachim of Sechach Pasul valid for a small Sukah? Even
one Tefach of Sechach Pasul should invalidate the entire Sukah which is only
7 by 7 Tefachim! We learned earlier that Sechach Pasul that is not mixed
together ("Chavtan") with valid Sechach cannot become Batel to the valid
Sechach and remains Pasul (9b; see Tosfos 15b, DH v'Ha, and Insights to 15).
Lavud cannot apply because it is not open space; when there is something in
the space, the principle of Lavud cannot apply to join what is on each side.
If so, even when there is only one Tefach of Sechach Pasul, it should not
become Batel to the rest of the Sechach, and as such, there are no longer 7
Tefachim of valid Sechach to make a valid Sukah!
(a) A Sukah does not have to be completely covered with Sechach to be valid.
It just has to have more shade than sunlight. In this case, the invalid
Sechach is only a minority while the valid Sechach is a "Rov," and thus the
Sukah is covered with valid Sechach which has more shade than sunlight. (The
area of the invalid Sechach is not worse than small gaps in the valid
Sechach, which are ignored as long as there is more shade than sunlight.)
However, if the only consideration is that there be more shade than sunlight
from the valid Sechach, then even if there are 3 Tefachim of Sechach Pasul,
the Sukah should still be valid, because there is still a majority of valid
Sechach (4 Tefachim) which means that there is more Sechach-shade than
It must be that Rashi means that when there are 3 Tefachim of Sechach Pasul,
or 3 Tefachim of open space, then we say that it is not considered to be
just a gap in the Sechach that can be ignored, but rather it is a self-
contained area which cannot be viewed as part of the Sechach at all. (M.
(b) RABEINU CHANANEL explains the Gemara in an entirely different manner. He
explains that in a small Sukah, the Shi'ur of Sechach Pasul that will
invalidate the Sukah is not 3 Tefachim, but rather 4 Tefachim (that is,
anything more than 3 1/2 Tefachim, or a majority of the Sukah). He learns
that as long as there is more shade than sunlight from the valid Sechach,
then the minority of Sechach Pasul will never be able to invalidate the
Sukah. It will never be like open space which invalidates a Sukah with just
Rabeinu Chananel explains that when the Gemara asks that in a small Sukah,
the Shi'ur of Sechach Pasul and open space needed to invalidate the Sukah
are the same, it does not mean that they both are defined by the exact same
number of Tefachim. Rather, it means that both Pesulim are measured in the
same units -- that is, Tefachim and not Amos. Since both are measured in
Tefachim, they are considered to be the same Shi'ur. In contrast, in a large
Sukah, Sechach Pasul will only invalidate the Sukah when there are 4 *Amos*
of the Sechach Pasul, which is not determined by the same unit of
measurement as is used by the Pesul of open space (3 *Tefachim*).
However, according to Rabeinu Chananel, how does the Gemara attempt to prove
that different Shi'urim are Mitztaref from the Mishnah that says that
different types of materials join together to make the minimum Shi'ur to be
Mekabel Tum'ah? In that Mishnah, all of the Shi'urim are measured in
Tefachim! They are thus considered to be the same Shi'ur according to
Rabeinu Chananel, and there is no proof that *different* Shi'urim can be
The answer is that the Mishnah there (Kelim 27:2) also mentions the Shi'ur
of 3 x 3 *Etzba'os* for a Beged to become Tamei with Tum'as Mes. Even though
our Gemara leaves out that part of the Mishnah, Rabeinu Chananel does quote
it. He explains that when the Mishnah says that a Beged is Mitztaref with a
Sak, it means even a Beged which is measured in units of Etzba'os (i.e. a
3x3 Beged which is Metamei only Tum'as Mes) can join a Sak to make a Shi'ur
of 4x4 Tefachim. We see from there that even Shi'urim which are measured in
different units, can still be Mitztaref.