Today’s section is a direct continuation of yesterday’s section, which attempted to offer a midrash as to why skhakh must grow from the ground and not be susceptible to impurity. The last midrash we encountered compared the skhakh to animal sacrifices offered on the holiday—just as the animal grows from the ground and (while alive) is not susceptible to impurity, so too skhkakh must grow from the ground and not be susceptible to impurity.
The problem with deriving the laws of skhakh from the laws of the festival offering is that this leads to the conclusion that skhakh too must be an animal. Obviously this is absurd so this midrash is rejected.
The Torah says that one should celebrate the festival of Sukkot during the time of year when one harvests one’s grain and grapes to make wine. Ravin reads this verse midrashically as if it says to build sukkot out of the left over products of one’s grain and grape harvest. This would mean that skhakh should grow from the ground and not be susceptible to impurity, since only the food part of the harvest is susceptible to impurity
The Talmud asks why we don’t read the verse as mandating the use of the actual product from the threshing floor and wine press. Why do we think it is just the waste product, which is not susceptible to impurity?
R. Zera answers that it would obviously be impossible to use actual wine as skhakh. Therefore we must interpret the verse to mean the waste from the winepress and threshing floor, which is not susceptible to impurity.
R. Yirmiyah objects that we could still interpret the verse as referring to food products. We could interpret “winepress” as referring to solidified wine coming from the region of Senir, which is similar to fig-cakes. Such material is susceptible to impurity and could be used as skhakh (although I wouldn’t want to sit in a sukkah with congealed wine as my cover!).
R. Zera laments that he thought they had an answer to the source of the halakhah that skhakh must be from the ground and not susceptible to impurity, but after R. Yirmiyah’s difficulty, we have no answer.
Not to worry, R. Ashi comes to the rescue! The Torah uses the word “from” before threshing floor and winepress. This implies that the skhakh must come from them but not be their main product—the actual wine or grain.
In the book of Nehemiah, after returning to Israel and renewing the covenant, Ezra reads in the Torah and tells the people to go out to the mountain and use these species to build a sukkah. These branches grow from the ground and are not susceptible to impurity.
The problem the rabbis have with the verse is that it mentions myrtle twice, since the rabbis consider the “thick tree” to also be a myrtle tree (see Leviticus 23:40).
R. Hisda therefore interprets the verse to refer to both mitzvot—the sukkah and the lulav. One type of myrtle, the wild myrtle, was to be used for the sukkah since all branches can be used as skhakh. The other type of myrtle, the one referred to in the Torah, was to be used for the lulav.
 It seems that this is how Ezra understands what one is meant to do with what we call the “four species.” Normative, rabbinic tradition, considers this a separate mitzvah, not connected to the building of a sukkah.
Today’s section begins with a new mishnah.
The Talmud will offer various explanations as to why these things cannot be used for skhakh. Once any of them is untied, they are valid for skhakh because they all grow from the ground and are not susceptible to impurity.
The final section teaches that everything that is invalid for the skhakh is valid for the walls. When it comes to the walls all we are concerned about is that there are walls—we are not at all concerned with the material of the walls.
R. Yaakov heard R. Yohanan his teacher explain two mishnayot but he’s not sure which explanation goes with which mishnah. The first mishnah is the one above. The other mishnah is one we will encounter later in this chapter. It teaches that if one hollows out an empty space in a haystack one cannot use the empty space as a sukkah.
There are two reasons given for these mishnayot. The first is that one shouldn’t make his store house into a sukkah. The second is that one must actively make his sukkah. The sukkah shouldn’t be made on its own.
Now since this is a decree lest one use his store-house [as a Sukkah] the other must have been forbidden on the ground of ‘you shall make’ [which implies], but not from that which is made.
R. Yirmiyah now tries to sort out which explanation goes with which mishnah. R. Yirmiyah is familiar with another tradition stated by R. Yohanan which explains that one cannot use these bundles as skhakh lest one store his bundles up there and then later on decide to use it as his sukkah. It looks as if this is actually the other reason, “you shall make, but not from that which is made.” Rashi explains that there are actually two levels of prohibitions here. From the Torah it would be prohibited to put bundles on the sukkah and then change one’s mind and untie them to use them as skhkakh. This would indeed be a violation of the principle, “You shall make, but not from that which is made.” Since this is a toraitic prohibition, the rabbis decreed that one can never use these bundles as skhakh, even if one put them up there to use as skhakh from the outset. This is understood as “lest one make one’s storehouse into a sukkah.”
Since this mishnah is explained by the principle of “lest one make one’s storehouse into a sukkah” the other mishnah, about digging in a haystack, must be explained by the reason “you shall make, but not from that which is made.” If one digs in a haystack and then uses the empty space as his sukkah, he didn’t actually make a sukkah. Meaning he didn’t put skhakh on top of his sukkah. Rather, he created negative space and it just turned out that he had skhakh above his head. This is not considered making a sukkah.
The Talmud explains that R. Yaakov hadn’t heard this statement of R. Hiyya b. Abba. That’s why he didn’t know which explanation went with which mishnah.
This section continues to deal with the explanation of the two mishnayot: 1) the prohibition of using bundles of wood for the skhakh; 2) the prohibition of making a sukkah by hollowing out a haystack.
R. Ashi disagrees with R. Yirmiyah’s analysis. He holds that both reasons apply to both mishnayot. Using bundles of straw is prohibited because it looks like a storehouse and because one might first put it up there and then change one’s mind and untie it, thereby violating the principle, “You shall make, but not from that which is already made.” Hollowing out a haystack also looks like a storehouse and it also violates the “you shall make” principle.
The Talmud responds on behalf of R. Yohanan why he explained the two mishnayot he did. R. Yohanan picked up on small cues from the language of the two mishnayot. When our mishnah said, “one may not use them as skhakh” it meant from the outset (lehathilah) one shouldn’t use them. But if one did, the sukkah is still valid. This type of halakhah is a “decree (gezerah)”—one shouldn’t do something, but if he did, his act is still valid. The other mishnah uses the language “it is not a sukkah.” This means that even according to toraitic law it is not a sukkah. This type of halakhah is one that would come from a midrash on the Torah such as “You shall make, and not from that which is already made.”