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ANSWERS TO REVIEW QUESTIONS

prepared by Rabbi Eliezer Chrysler
Kollel Iyun Hadaf, Jerusalem

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Eruvin 78

Questions

1)

(a) A ledge of four square Tefachim protruding from a wall of *more* than ten Tefachim is not sufficient to reduce the height of the wall.

(b) A ladder, even one that is *less* than four Tefachim wide, leaning against the ledge (but not against the wall next to it) will be considered a Pesach.

(c) The two ledges that protrude from a twenty Tefachim wall must be placed, one below ten Tefachim - with a ladder leaning against it, and the other, above ten Tefachim. The ledges must be placed apart from each other, in a way that allows for a ladder to be placed from one to the other.

2)
(a) When Rav Huna says that a pillar ten Tefachim tall and four Tefachim square that is stuck in the street, becomes reduced when one sticks a peg in it - he is referring to the *width* of the pillar of four by four, the minimum width for a Reshus ha'Yachid. By sticking a peg in it, one reduces its width, so that it is no longer a Reshus ha'Yachid.

(b) Rav Ashi says 'Afilu she'Gavo'a Sheloshah' - because he holds that a peg of three Tefachim can be used to hang things on, and consequently, it is Chashuv and will not detract from the four Tefachim space (since one can now use both the remaining space and the space taken up by the peg).

(c) When they asked Rav Ashi whether the same would apply if the top of the board was full of pegs - he replied that one would also be Chayav, since one could put things across the top (like one combines the earth lying round a pit with the pit itself to make up four Tefachim width - even though the only way they can be used together is by placing things across the top).

3)
(a) Rav Yehudah quoting Shmuel requires a ladder of fourteen Tefachim, to reduce the height of a ten Tefachim wall - because if the angle of the ladder would be more acute than that, it would be difficult to climb, in which case, it would not be considered a Pesach.

(b) Rav Yosef permits even a ladder of thirteen and a bit - because according to him, it will suffice, if the ladder reaches within the *top Tefach* of the wall; whrereas Abaye permits even eleven and a bit, because he holds that it only needs to reach within *three Tefachim*.

(c) Rav permits even a ladder of seven Tefachim and a bit, following the leniency of Abaye, in addition to permitting a ladder even when it is completely erect.

(d) Shmuel compared the ladder to the case of two platforms, one on top of the other, which we permitted above (on the previous Amud).

4)
(a) Both large sections of date-palm stumps and Babylonian ladders - qualify as a Pesach even if they are not attached - because they are heavy.

(b)

1. The Amora who says this by Babylonian ladders, will certainly include date-palm stumps;
2. Whereas the one who says it by date-palm stumps will not include Babylonian ladders - presumably, either because they are not as heavy as the stumps, or because they are easier to transport.
(c) If two ladders (neither of which is two Tefachim wide) are placed near each other, and one adds straw in between the adjacent rungs of the two ladders to join them together (thereby making up the four Tefachim) - this will not constitute a Pesach, since the new straw rungs are too weak to hold one's weight.

(d) In the reverse case however, when one places a wooden ladder in between a series of straw rungs, to make up four Tefachim - this will constitute a Pesach, since it is possible to climb the rungs of the ladder and to hold the straw section to help him climb.

78b---------------------------------------78b

Questions

5)

(a) One would need to carve rungs in the wall ...
1. ... only up to a height of ten Tefachim high to widen the rungs of a ladder that were not four Tefachim wide.
2. ... if there was no ladder - right up to the top of the wall.
(b) This is because - in the former case, where he already has a ladder going up to the top, it is sufficient to make up the deficiency in width, by carving rungs up to the height of four Tefachim to help him begin to climb; once he reaches the height of ten Tefachim, it is easy to climb the remaining distance to the top, even though it is less than four Tefachim wide. Whereas in the latter case, where there is no ladder at all, and it will be difficult to complete the ascent even after the initial ten Tefachim, without anything to assist him, one requires rungs all the way up to the top.
6)
(a)
1. A tree might not be considered a Pesach, even according to Rebbi, who *validates* an Eruv on a tree - because that is only with regard to the Din of Eruv, which becomes effective during Beis Hashemashos, when, according to Rebbi, Rabbinical decrees (such as climbing trees) do not apply on Shabbos; whereas a Pesach must be a Pesach for the whole of Shabbos, which a tree is not.
2. On the other hand, it might be considered an Eruv, even according to the Rabbanan, who *invalidate* an Eruv on a tree - because that is only due to the fact that an Eruv has to be edible, albeit it only for the duration of Bein Hashemashos; whereas as far as a Pesach is concerned, it only needs to be called 'a Pesach' (which a tree *is* - during the week); who said that it must be usable on Shabbos?
(b) Rav Yosef's Sha'aleh by an Asheirah tree is - whether, even assuming that other trees *are* called a Pesach, that is because there is *no* Isur Hana'ah involved, whereas here there *is*.

(c) Maybe an Asheirah tree (and our Sugya is confined to one that is detached [see 7b] - Ritva) will not be called a Pesach, even according to Rebbi Yehudah, who *permits* placing an Eruv on a grave - because there (where Eruv Techumin is only permitted by a D'var Mitzvah, and where he is not concerned that the Eruv be preserved, once it is Koneh with the entry of Shabbos), he is deriving no benefit from it; whereas with regard to using an Asheirah-tree for Eruvei Chatzeros (which is permitted even when it is not for a D'var Mitzvah) - he *is*.

(d) Or it could be that, even according to the Rabbanan, who *forbid* placing an Eruv on a grave - the Asheirah-tree will still be considered a Pesach, since it really is a Pesach (with regard to gentiles), which has 'a lion riding on it' (i.e. an external reason - the Isur Shabbos, that is preventing its use).

7)
(a) Rabah replied 'Ilan Mutar, va'Asheirah Asurah'.

(b) Rav Chisda maintains - that the tree (which is Asur because the Isur is one of Shabbos) should be Asur; and the (detached - see 6c) Asheirah, which has nothing to do with the Isur of Shabbos) should be permitted.

(c) Rav Nachman bar Yitzchak, disregarding the previous Sugya - explains that whether or not, a tree is considered a Pesach, is a Machlokes Rebbi and the Rabbanan (Rebbi, who permits placing an Eruv Techumin on a tree, will also consider a tree to be a Pesach; the Chachamim, who forbids it, will not). And an Asheirah -tree is a Machlokes Rebbi Yehudah and the Rabbanan (Rebbi Yehudah, who permits placing an Eruv on a grave, will also consider an Asheirah to be a Pesach; the Rabbanan, who forbid it, will not). Note: According to Rav Nachman bar Yitzchak, a Pesach follows the same pattern as an Eruv, and must therefore be practically usable (at least during Bein Hashemashos).

8)
(a) For a dividing-ditch between two courtyards, to cause the two courtyards to be obligated to make two separate Eruvin - it must be four Tefachim wide, and it must run all the way across the Chatzer.

(b) If the ditch is filled with ...

1. ... straw or stubble - it will *not* be considered filled (since these commodities are usable and stand to be removed.
2. ... earth or stones - it will, since earth and stones are normally placed in a ditch to remain there.
(c) If one fills the ditch with earth - the two courtyards combine, so that one may only make a combined Eruv; whereas when a plank is placed across them, it has the Din of a Pesach, leaving them with the option of either combining to make one Eruv, or of making two separate Eruvin.

(d) The Mishnah writes that the same Din of joining the two courtyards with a plank, applies equally to two ledges that protrude from an upper floor of two adjacent houses - giving them the same option of making one combined Eruv or two separate ones, should they place a plank across from one to the other.

9) The Gemara differentiates between the straw *Mechitzah*, which is a Mechitzah (since a Mechitzah is a Mechitzah whether one is Mevatel it there or not), and the straw *in the ditch*, which constitutes a Chatzitzah, (and a Chatzitzah is only effective if one is Mevatel it to that place, not if it stands to be removed).

10) 'Bayis she'Mil'ehu Teven O Tzeroros, u'Bitlo, Batel' - is speaking about a house (i.e. a room) which contains something which is Tamei Mes (and therefore Metamei be'Ohel). As long as there is space in the house, the Tum'ah fills the house, but goes only as far as the ceiling. By filling it with straw and being Mevatel the straw there, one causes two things to happen, one le'Kula, and one le'Chumra: 1. That the Tum'ah is now confined to the space that is immediately above the Tum'ah (but not to the rest of the house); 2. The Tum'ah now goes up beyond the ceiling, to the sky.

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