Shiur summary (draft from the recording)
Supporting schach on bed posts: R' Yehuda's reason
הסומך סוכתו בכרעי המטה
Sukkah 21b · Wednesday, November 5, 2025
The sugya
The Mishnah: one who rests his sukkah (schach) on the posts of a bed, kosher; R' Yehuda says if it cannot stand by itself, it is pasul. The Gemara brings a machlokes R' Zeira and R' Abba bar Mamal on R' Yehuda's reason: no keva (a bed is portable), or that it is supported on a davar hamekabel tumah. A nafka minah is iron spits planted in the ground. Abaye limits the Mishnah to samach, leaning on the bed, but al gav hamitah is kosher according to both reasons. The Rebbi ended by noting that the Gemara never gave the reverse nafka minah and left it to the chabura to think of one.
Step by step (shakla v’tarya)
- MishnahHaSomech sukkaso b'kar'ei hamitah: schach placed on the bed posts is kosher according to the Chachamim. R' Yehuda says if it cannot stand by itself it is pasul.
- Kar'ei hamitah means bed posts. The bed has a head, a foot and a side, and one puts the schach right on top. The Chachamim say no problem.
- GemaraMai ta'ama d'R' Yehuda? Why does he say it is pasul?
- MachlokesR' Zeira and R' Abba bar Mamal argue in his reason. We do not know who says which.
- ShitahOne says: because it has no keva. A bed is portable furniture, and schach has to be on something that will not move around.
- ShitahThe other says: because he supports it with a davar hamekabel tumah. A bed is furniture and is mekabel tumah.
- GemaraMai beinaihu? The Gemara looks for a practical case where one reason would make R' Yehuda allow it and the other would not.
- GemaraThe case: he planted iron spits vertically, with separate walls, and put the schach on them.
- GemaraUnder the keva reason this has permanence, so no problem. Under the mekabel tumah reason it is still pasul, because the schach is supported on something mekabel tumah.
- The RebbiAlthough R' Yehuda only said you cannot put it on a bed, it is important to know why, so that we can judge other cases.
- GemaraAbaye: lo shanu ela samach. The Mishnah's psul according to R' Yehuda is only when the schach is leaning on and supported by the bed.
- GemaraAval sikech al gav hamitah, kosher.
- The RebbiAl gav: the bed serves as the walls, and the schach is held up by separate kosher supporting poles that stay in place. If you pulled the bed away, the schach would not fall.
- The RebbiIn the kosher case the separate poles cannot be metal; they have to be wood.
- The RebbiThe poles must go into the ground. If they go into the bed, you still have the problem, since the bed is movable.
- GemaraThe Gemara explains: under the keva reason, here there is keva, because the schach is not going anywhere.
- GemaraUnder the mekabel tumah reason, here with a separate structure around the bed, he is not supporting it on a davar hamekabel tumah. So it is kosher according to both.
- The RebbiWhy does the Gemara spell out what is obvious? Sometimes the Gemara gives extra lines that are easy to understand. It is geshmak.
- The RebbiThe Gemara gave one case kosher only by the keva reason (iron spits) and one case kosher by both (al gav). It never gave a case kosher by the tumah reason but pasul by the keva reason.
- It should not be hard to think of such a case. The chabura should think about all the variables.
Kashas
- Mai ta'ama d'R' Yehuda: why is schach resting on bed posts pasul?
- Why does the Gemara spell out the reasoning for al gav hamitah when it is obvious once we know the two reasons?
- Why is there no case given where the schach is kosher by the tumah reason but pasul by the keva reason?
Teirutzim
- One Amora: the bed has no keva, since it is portable.
- Other Amora: it is supported on a davar hamekabel tumah.
- Sometimes the Gemara gives extra lines that are easy to understand. It is geshmak.
The Rebbi’s chiddushim
- The real psul of kabbalas tumah is a schach issue: you cannot use furniture as schach. Since the bed supports the schach, its being mekabel tumah also matters. Whether this was said in the name of Rashi is unclear in recording.
- Practically, even with perfectly good schach, there are requirements about what you may lay it down on.
- His own sukkah: a metal pergola frame with walls around it. The schach was an issue because of the metal, so they laid 2x4s on top and put the schach on those.
- 2x4s are probably peshutei kelei etz and not mekabel tumah. Any metal is mekabel tumah, he thinks. A bed is a real kli, a piece of furniture.
- Knowing the reason behind R' Yehuda's psul lets us judge new cases.
- In answer to a question: something that has already become a finished kli is mekabel tumah. An unfinished piece in a factory may not be.
- A shiur he heard explained the case as taking a bed, throwing away the mattress and springs, and using the ready-made kli as three walls of the sukkah.
- The definition of al gav: if the bed were pulled away, the schach would not fall. Schach merely touching metal is fine; schach supported by metal is no good.
- The Gemara never gave the reverse nafka minah (kosher by the tumah reason, pasul by the keva reason). It should not be hard to find one.
Unclear in recording
- Whether the explanation that kabbalas tumah is really a schach problem was attributed to Rashi.
- The exchange with a talmid about unfinished keilim and whether they are mekabel tumah is largely garbled.
- The discussion of the diagram cases (metal case, raised poles, samach mamish) is garbled.
- The discussion of a canopy bed and a wooden pergola is unclear. The Rebbi said he does not know whether R' Yehuda would allow these.
Drafted from the recording of the shiur, for chazarah. Torah terms follow the Rebbi’s own words; anything that could not be made out is marked “unclear in recording”. Tap a time to hear that point. Corrections welcome.