Sukkah 018

9:
We now come to the second clause of our mishnah. This is the clause that, at first glance, seems to be some kind of conundrum. It will be easier, perhaps, to understand what the sages are trying to say here if we first give an example.

10:
David is travelling from Caesarea to Emmaus, where he intends to spend the week of the Sukkot festival with relatives. (Caesarea was a port city with a mainly non-Jewish population and a large Jewish minority; Emmaus was an inland spa town, known for its easy living.) Unfortunately, while still on the road a wheel falls off of David's cart and it will take time to mend. He realizes that he will have to spend at least the first day of the festival while still on the road. He cannot erect his sukkah on his cart because it is no longer stable. Knowing that the area through which he is travelling is rife with bandits he decides to build his little sukkah up a tree rather than risk being attacked on the ground. David chooses a tree with rich foliage in which to build his sukkah.

11:
You will recall that we have learned on several occasions that, unlike the s^ekhakh of a sukkah, the panels of a sukkah may be made from plants, leaves, boughs — almost anything from the vegetable world — which is still attached to the soil. So, to save time and energy, David decides that the greenery of the tree will form one or more of the panels of his makeshift sukkah.

12:
The first option described in our mishnah is

Ideally, the sukkah must have three or four panels. If two of the panels are formed by the branches of the tree and one more panel is set up in the tree by David the sukkah is a valid sukkah. However, because we are not allowed to climb trees on YomTov David could not use his sukkah on the first day of Sukkot. The same would apply of only one of the panels was formed by the tree and the other two were made by David: the sukkah would be valid but it could not be used on YomTov.

13:
At the end of our mishnah comes a kind of general rule:

Therefore, if David wants to use his sukkah on the first day of the festival he must make sure that three of the panels are set up by him in the tree. Then, even if the fourth panel is part of the tree, the sukkah is valid and can be used on YomTov. This is because even if one were to remove the tree, as it were, the sukkah with its three panels would still be a valid sukkah.

14:
It is worthwhile to note the exact wording of our mishnah:

The sukkah, to be valid, must be at the top of the tree. The s^ekhakh must be separate from the tree and none of the branches of the tree should overhang the s^ekhakh.

15:
The creation of a sukkah in a tree is rather difficult for us to imagine. In his commentary on our mishnah Rabbi Ovadya of Bertinoro explains who he thinks it must be done: