Detached Or Unrelated
‘He Made an Asheirah Tree Into a Ladder…’
(Eruvin 78b)
The Torah (Devarim 7:5, 12:3) forbids deriving benefit from an asheira tree; thus, it’s biblically prohibited to use an asheira tree as a ladder to scale a wall.
The Sages (Eruvin 100a) forbade climbing trees on Shabbos lest one break off a branch and violate the biblically prohibited melacha of kotzer – plowing or reaping (Shabbos 107b, 108a based on Shemos 34:21).
The Gemara questions whether branches of a tree growing along a wall can serve as a natural ladder to create a pesach (a portal, enabling two separate courtyards abutting the wall to join in an eruv). The Gemara questions as well whether an asheira can serve as a pesach.
The Invisible Lion
R. Chisda maintains that an asheira that borders a wall can serve as a pesach even though it’s biblically prohibited to climb the asheira. He likens the biblical prohibition to climb an asheira tree to a lion crouched near a doorway preventing passage through the door. He reasons that even though it’s forbidden to use the pesach created by the asheira, it’s a pesach nonetheless just like a doorway with a threatening lion is a pesach in spite of the danger involved in using the door.
R .Chisda limits his reasoning to prohibitions that are unrelated to Shabbos. If a Shabbos-related issur prevents passage through the doorway or passage over the wall, the chatzeiros cannot join for an eruv. Therefore, he says an ordinary tree cannot serve as a pesach because climbing the tree is prohibited due to a Shabbos-related issur.
Two Issurim
The Ritva (ad loc.) points out that climbing an asheira tree on Shabbos, in addition to the issur of benefiting from avodah zarah, also involves the rabbinic ban against climbing trees on Shabbos. Hence, he asks why R. Chisda ignores this Shabbos-related issur and validates a pesach created by an asheira.
Where Detached
He answers that the Gemara is referring to an asheira that is detached from the ground, and the issur of climbing trees doesn’t apply to a detached tree (because if a person were to detach a branch from a detached tree, he wouldn’t violate the melacha of kotzer).
It Transcends Shabbos
Rabbi Akiva Eger suggests an alternative answer. He argues that the rabbinic issur to climb trees on Shabbos doesn’t apply to an asheira (even when attached to the ground). Why? Because we’re not concerned that a person will mistakenly break off a branch from such a tree on Shabbos since he’s biblically proscribed from deriving benefit from it (even during the week) due to the issur of avodah zarah.
Therefore, the only issur involved in climbing an asheira on Shabbos is benefiting from the avodah zarah, which is not a Shabbos-related issur.