Eruvin 33 - Eruv on a tree
As we learned, one cannot go farther than two thousand steps away from his city of residence on Shabbat, and if he wants to go further, he needs an eruv - food that will symbolize that he moved his dwelling to this new place.
However, if he placed his eruv on a tree, he has a problem. The Sages prohibited taking objects from a tree on Shabbat, and therefore his eruv food is not accessible to him and is invalid. Nevertheless, the ruling is different and states that if the eruv is on a tree above ten hand-breadths from the ground, the eruv is indeed invalid, but if it is lower than that, it is valid.
How can we explain this? First, we are forced to say that this must be the opinion of Rabbi Yehudah the Prince, who says that at twilight the laws of the Sages do not apply. The tree is not muktzeh, and he can take his eruv. If so, why does ten hand-breadths make a difference? Well, the tree itself is similar to a house and is a private domain. When he takes his food from it and brings it to himself in the public domain, he violates Shabbat, and since he cannot do that, his eruv is invalid. However, below ten hand-breadths people usually do not carry, such area is called a "karmelit", its prohibition is lighter, and his eruv is again valid.
Art: Vincent Van Gogh - Autumn Landscape with Four Trees
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