I have a question on the following Gemarah.
First the Gemarah tells us that if we have two "Koros" and in each one measures a bit less than a Tefach, and in between them we have up to 3 tefachim, one can use them both as if it was one "Kurah", only if it could hold an "Arich" on it.
My question is, if we look at the Gemarah latter on (A few lines latter). We see that if we have a Korah that is 4 Tefachim, we don't need it to hold an "Arich", like in a case of straw. If so, why previously, when dealing with two Kuras(each a bit less than a Tefach) and with a space of 3-4 tefachim in between, why don't we say here the Din of "Livud" and say that it is as if we have a Kurah of at least 4 tefachim, and thus we shouldn't care if they could hold an Arich or not. Why does the Gemarah require those two Kuras to hold the Arich?
I hope the question is understandable.
First, it is Rebbi Yehudah who says that a Korah made of straw is valid because "we view it as if it was made of metal." The Rabanan in the Mishnah, though, argue with him.
Furthermore, the Beraisa is referring to two Koros neither of which has a width sufficient enough to support an Ari'ach. But if the two together have a width that can support an Ari'ach, we join them together. The Beraisa is not referring to the strength of each Korah.
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