Sukkah 17a (יז.) — the Talmud in English

Mishna:

The Mishna before us explains the halakha of dofen akuma (“a bent wall”) in three different ways.

The common feature of all three cases is that the walls are distant from the sekhakh.

Whenever the walls are distant from the sekhakh—for example, when there is airspace measuring three tefahim between the walls and the sekhakh—the sukkah is invalid.

However, wherever the halakha of dofen akuma applies, the walls are considered adjacent to the sekhakh, as will be explained.

The Mishna begins by explaining the disqualification of walls that are distant from the sekhakh:

If one moved the roofing away from the walls

toward the center of the sukkah

three tefahim,

it is

invalid,

because airspace invalidates the sukkah when it measures three tefahim.

The Mishna continues by explaining three cases in which the halakha of dofen akuma validates the walls, so that they are considered walls adjacent to the sekhakh.

a.

A house whose roof has collapsed

in its center, at a distance from the walls on every side,

and one covered it with sekhakh

over that area where the roof had collapsed, while the part of the roof that had not collapsed intervened between the roofing in the center of the roof and the walls,

if there is

a distance

from the wall

of the house, which serves as the wall of the sukkah, to

the roofing

in the center of the house,

four cubits,

it is

invalid.

But if the distance between the sekhakh and the walls of the house is less than four cubits, the sukkah is valid.

The amoraim in the Gemara disagree about the reason for this: One opinion holds that the measure of invalid roofing that invalidates a sukkah wherever it is placed is four cubits, whether the invalid roofing was placed in the middle of the sukkah or at its side.

Another opinion holds that the measure of invalid roofing that invalidates a sukkah is four tefahim. However, if the invalid roofing was placed at the side, adjacent to the wall, it does not invalidate the sukkah until it is four cubits wide. This is because there is a halakha given to Moses at Sinai that invalid roofing placed at the side, adjacent to the walls, is to be considered as though it were part of the wall that bent and curved upward, and consequently the walls are found to be adjacent to the sekhakh [this halakha is called “dofen akuma”], and one who sits beneath the invalid roofing is considered to be sitting beneath the wall.

b.

Likewise,

the measure of the distance applies to

a courtyard surrounded by a colonnade

on three sides.

That is, there was a house built in the shape of the Hebrew letter het, with a courtyard in its center.

Around the house, between the house and the courtyard, there was something resembling a balcony, with a roof above it. This balcony [called an akhsadra] was open toward the courtyard and surrounded it on three sides.

If one placed sekhakh over the open area of the courtyard enclosed by the akhsadra, and the walls of the house served as the walls of the sukkah in the courtyard, while the roof of the akhsadra, which is invalid roofing, separated between the valid sekhakh and the walls of the house, which now served [on their outer side] as the walls of the sukkah, on their outer side—

then, if the roof of the akhsadra was four cubits wide, the sukkah in the courtyard is invalid, because the walls of the house, which are the walls of the sukkah, are four cubits distant from the sekhakh. But if the distance between the sekhakh and the walls is less than four cubits, the sukkah is valid, because we view the roof of the akhsadra as part of the wall that bent and reached the sekhakh.

c. Likewise,

a large sukkah that was surrounded

on its roof, around it and adjacent to the walls,

with something unsuitable for roofing, if beneath it there is

beneath that invalid roofing a width of

four cubits,

the sukkah is

invalid.

Gemara:

The Gemara asks:

All these

three cases in which our Mishna stated the law of dofen akuma,

why do I need them?

Is there a novel point in each one that is not present in the others?!

The Gemara explains:

It is necessary!

Had it taught us

the law of

a house whose roof has collapsed

alone, we might have said that the halakha of dofen akuma was stated specifically in this case, to associate the partitions of the house with the sukkah in the center of the house,

because these partitions

are

for the house

in which the sukkah was made that they

were made for.

These partitions were made for the needs of the house, and it is this house that was made into a sukkah. Therefore, the halakha was stated to regard these walls as the partitions of the sukkah through dofen akuma.

But in

a

courtyard surrounded by an akhsadra,

where one placed sekhakh over the open area of the courtyard surrounded by the akhsadra,

the partitions

of the house that one wishes to associate with the sukkah in the courtyard through dofen akuma

were not made for the akhsadra [

they were not made for the outer akhsadra’s needs], but for the needs of the house;

perhaps not

was the halakha of dofen akuma stated to regard the walls of the house as part of the sukkah. Therefore

it is necessary:

our Mishna had to teach us that the halakha of dofen akuma applies even in a courtyard surrounded by an akhsadra.

And had it taught us

only

these two,

these two laws—of a house whose roof has collapsed and of a courtyard surrounded by an akhsadra, in which we say dofen akuma—we might have said that the halakha of dofen akuma applies specifically in those cases

because their roofing,

the roofing that intervenes between the valid sekhakh and the wall, is of the

same type as valid roofing,

for the roof of the house and the roof of the akhsadra are also made of boards that are not susceptible to ritual impurity and do not grow from the ground. Their only deficiency is that they were not made for the sake of a sukkah but for the sake of dwelling, and they are invalid because of the principle “You shall make it, and not that which is already made.”

But a large sukkah that was surrounded

above, between the walls and the valid sekhakh,

with something unsuitable for roofing,

such as types of metal, which are susceptible to ritual impurity and do not grow from the ground,

whose roofing

that intervenes between the valid sekhakh and the wall is of the

same type as invalid roofing—perhaps we will not

validate it by means of dofen akuma. Therefore

it is necessary

for our Mishna to teach this halakha even with regard to a sukkah surrounded by invalid roofing.

Rabba said: I found

among

the scholars of Rav’s academy [

the members of Rav’s academy],

who were sitting and saying

in Rav’s name:

a. Airspace invalidates

even a large sukkah

by three

tefahim.

b.

Invalid roofing invalidates

even a large sukkah

by four

tefahim.

That is, this is a sukkah with only three walls, and airspace or invalid roofing crossed it along its entire length. If that airspace was three tefahim wide, or if that invalid roofing was four tefahim wide, they invalidate the sukkah, because this intervening strip divides the sukkah in two, and each of the sections of the sukkah is consequently left with only two walls.

I said to them [

I challenged their words],

“As for airspace that invalidates by three

tefahim,

from where do you know this [

what is the source for you]? It is because

we learned

in our Mishna:

If one moved the roofing away from the walls three tefahim

the sukkah is

invalid.

From this you learned that airspace invalidates a sukkah at three tefahim.

If so, the same should apply to

invalid roofing as well: it should not invalidate

the sukkah

except at four cubits,

and not as you said, at four tefahim.

We learned

in our Mishna:

A house whose roof has collapsed

in its center

and one covered it with sekhakh

over that collapsed area, while the roof of the house intervened between the valid roofing placed in the center of the roof and the walls of the house serving as the walls of the sukkah

; if there is between the roofing

that is valid

and the wall

of the house

four cubits,

it is

invalid.

It would apparently be clear from this that invalid roofing does not invalidate the sukkah until four cubits”?!

And they said to me,

the members of the academy:

“Except for that passage” [

apart from this clause]. That is, one cannot prove from our Mishna that invalid roofing does not invalidate a sukkah until four cubits,

for Rav and Shmuel both said

in explaining the reason for the Mishna:

“It concerns dofen akuma,”

which validates it. That is, the reason for the validation is not that invalid roofing does not invalidate until four cubits. Rather, by the law of dofen akuma, we view the invalid roofing placed at the side as part of the wall that bent and curved upward, and consequently the walls of the sukkah are found to be actually adjacent to the sekhakh.

I said to them

to challenge their words further:

“What would be the law if there were invalid roofing less than four

tefahim wide in the center of the sukkah,

and

next to it there was

airspace less than three

tefahim wide, so that the invalid roofing by itself does not have the measure that invalidates the sukkah, and the airspace by itself likewise does not have the measure that invalidates the sukkah?

What

do you say about this sukkah?—that it is

valid!

But if one

filled it

that airspace of less than three

with skewers,

which are unfit for roofing, thereby completing the measure of four tefahim of invalid roofing,

what

do you say about the status of this sukkah?—that it is

invalid.

And how is this possible?!

And

is it possible that

there will be no air,

the more stringent factor,

which disqualifies [a sukka] with three

handbreadths,

like invalid roofing,

the less stringent factor,

which disqualifies [it] at four cubits?!

How can it be that at first, when that area was not covered at all, but consisted only of air—which is more stringent and disqualifies a sukka with three handbreadths—the sukka was valid, whereas now, when it has become invalid roofing, which is less stringent, the sukka is disqualified?!

And they said to me

the Sages of Rav's academy:

If so,

if this is impossible, then

according to you, who say that invalid roofing disqualifies

everywhere

at four cubits as well,

the same question can also be raised:

And

what if there is invalid roofing less than four cubits

which does not disqualify the sukka,

and

beside it there is

air less than three

handbreadths,

what

do you say about it, that it is

valid!

But if

you fill

that airspace

with rods,

and complete the measure of four cubits,

what

do you say about it? That it is

invalid!

This poses a difficulty for you:

air will not be

the more stringent factor,

which disqualifies at three

handbreadths,

like invalid roofing,

the less stringent factor,

which disqualifies

at four cubits?!

And I said to them

to resolve their objection to my words:

What is this,

what comparison is this?!