Study Eruvin folio 100A with parallel Hebrew-English text, traditional commentary, and modern study tools. Free access to Babylonian Talmud online.
This was prohibited because it is a dwelling that serves only the air, i.e., it is used only by someone guarding the fields or the like. It is not used as permanent living quarters, despite its partitions. And the rule with respect to any dwelling that serves only the air is that it is not permitte
The Mishnah states: If the roots of the tree are 3 handbreadths above the ground, one may not sit on them on Shabbat. It was stated that amora’im disagreed with regard to the roots of a tree that rise up and then bend and come down from above, from a height of 3 handbreadths to within 3 handbreadth
The Talmud clarifies the rationale of each opinion. Rabba said that it is permitted to use them, as anything less than 3 handbreadths from the ground is considered as the ground. Rav Sheshet said: It is prohibited to use them; since they come from a prohibited source, they are prohibited. The sect
The Talmud proceeds to qualify the dispute: With regard to ascending and descending roots that resemble a rocky crag, those that rise upward are certainly prohibited according to all opinions; those that fall downward are permitted according to everyone. It is the roots that branch out to the sides
And likewise, Rabba and Rav Sheshet disagree about a tree that grows in a ditch that has elevated roots, some of which are concealed by the banks of the ditch. The amora’im dispute whether the roots concealed by the banks are considered part of the ground. And likewise, in the case of a tree that