QUESTION: Rav Huna rules that if one's animal is laden with glass utensils, one may place pillows underneath the animal on Shabbos and untie the straps so that the glass items fall down onto the pillows and do not break. The Gemara questions Rav Huna's ruling from the Mishnah, which states clearly that one may move utensils on Shabbos. The Gemara answers that Rav Huna refers to utensils that are Muktzah -- "Karnei d'Umna," the instruments of a blood-letter -- which may not be handled on Shabbos. RASHI explains that they are not fit for use on Shabbos because they are loathsome (Muktzah Machmas Mi'us).

Later (157a), the Gemara explains that the Halachah follows the opinion of Rebbi Shimon. Rebbi Shimon maintains that there is no such thing as Muktzah Machmas Mi'us. Why, then, does the Gemara suggest that Karnei d'Umna are Muktzah?

(a) The RASHBA explains that the instruments of a blood-letter are more repulsive than utensils that are Muktzah Machmas Mi'us. An old oil lamp, for example, which is dirty and disgusting, still has some useful purpose, for it can be used to cover a barrel if not for lighting. The instruments of a blood-letter, though, are so disgusting that no one would use them even to cover a barrel. This appears to be Rashi's intention here as well (DH d'Umni, "they are not fit for anything").

(b) The RITVA and BA'AL HA'ME'OR answer that the Karnei d'Umna are Muktzah because of Chisaron Kis (they are very delicate items), and not because of Mi'us. Rebbi Shimon agrees with the concept of Muktzah Machmas Chisaron Kis (157a).

(c) The RASHBA suggests that the Karnei d'Umna fall into the category of Kli she'Melachto l'Isur, a utensil whose primary usage is forbidden (since it is forbidden to draw blood on Shabbos), and therefore they may not be moved on Shabbos merely to save them from damage (124a).

(According to the Rashba, we may deduce that an item that supports a Kli she'Melachto l'Isur is considered a Basis l'Davar ha'Asur, since the Gemara says that the pillows onto which the Karnei d'Umna fall become unusable when they support Muktzah items).

OPINIONS: The Gemara cites a Beraisa that states that a Sukah comprised of two walls that were built by man and the third wall is a tree, it is a valid Sukah, but one may not enter it on Yom Tov, because he is not permitted to use a tree on Yom Tov. The Gemara attempts to prove from here that "Tzedadin" (the sides of a tree or animal) may not be used on Shabbos or Yom Tov.

In what way is the tree being used in this case?

(a) RASHI explains that the Beraisa refers to a case in which the roof (Sechach) of the Sukah is supported by the tree on one side. In what way does one use the tree when he goes into the Sukah? Perhaps sitting under the Sechach is considered usage of the tree, since the Sechach is partially supported by the tree.

(b) The RITVA argues and says that sitting under the shade of the Sechach is not called usage of the tree, because one certainly is permitted to sit in the shade of a tree on Shabbos and Yom Tov. Rather, the reason why one is considered to be using the tree in this case is because it was the normal manner for people to place their belongings on top of the Sukah when they entered.

This actually appears to be the intention of Rashi here (DH Shetayim) as well. TOSFOS here (DH Shetayim, in his first explanation) and in Sukah (22b) offers a similar explanation.

However, according to this explanation, the prohibition to use the Sukah on Yom Tov seems to be a Gezeirah l'Gezeirah. It is prohibited mid'Rabanan to use this Sukah on Yom Tov, lest one place his belongings on the Sechach, which itself is forbidden only because of a Gezeirah d'Rabanan. Apparently, it was very common for people to place belongings on top of a Sukah, and therefore the Chachamim considered this to be one Gezeirah ("Kula Chada Gezeirah Hi"). (M. KORNFELD)

(c) TOSFOS suggests a third explanation. He explains that the bottom of the Sukah is built on and supported by the top of a tree. Therefore, when one walks into the Sukah and walks on its floor, one uses the tree.

Tosfos in Sukah (22b), however, rejects this explanation and accepts Rashi's explanation instead, because it is implicit in the Gemara here that the roof (Sechach) of the Sukah, and not the floor of the Sukah, is part of the tree. What does Tosfos mean? How is this implied in the Gemara here?

1. Perhaps Tosfos infers this from the Gemara's conclusion that the tree that serves the Sukah is a bushy tree that does not touch the Sukah. If the tree is supporting the floor, what purpose does it serve if it does not touch it? If the tree serves as a wall, however, it can serve as a wall even if it does not touch any part of the Sukah or Sechach.

2. Second, the Gemara later concludes that the Tosefta, in which Rebbi Shimon ben Elazar argues with the Mishnah and permits one to go into a Sukah supported by a tree, refers to "Tzidei Tzedadin" (the sides of the sides of a tree) and not "Tzedadin." If the Mishnah refers to a tree that supports the roof of the Sukah, then the case in which the tree, which we considered until now to be Tzedadin, is considered Tzidei Tzedadin is easy to understand. For example, the tree supports a wall which, in turn, supports the roof (as Rashi writes in DH Amar Abaye). However, if the Mishnah refers to a tree that supports the floor of a Sukah, the tree is clearly an immediate support, "Tzedadin" and not "Tzidei Tzedadin." The Gemara cannot assert that the tree is only Tzidei Tzedadin without redefining the case of the Mishnah. (M. KORNFELD)