1) "KIL'AYIM" MADE FROM A HARD MATERIAL
OPINIONS: The Mishnah (14b) states that one is permitted to send a gift of clothing to his friend on Yom Tov even if the clothing contains a forbidden mixture of Kil'ayim. The Gemara asks that one may send a gift on Yom Tov only when the item is fit for use on that day. Since a garment of Kil'ayim is forbidden to be worn, why may one send it to his friend on Yom Tov? The Gemara concludes that the Mishnah refers to Kil'ayim made from a hard material. Since it is made from a hard material, the prohibition against wearing Kil'ayim does not apply.
When is one permitted to benefit from Kil'ayim made from a hard material?
(a) The RA'AVAD (on the Rif) explains that, mid'Oraisa, the prohibition of Kil'ayim does not apply to a hard material. Mid'Oraisa, one is permitted even to wear such Kil'ayim. The Rabanan, however, prohibited one from wearing it, but they did not prohibit one from lying or sitting on it. Mid'Oraisa, one is prohibited from wearing a soft material of Kil'ayim, and the Rabanan prohibited one from lying or sitting on it. If the material is a bit soft and a bit hard, one is prohibited to wear such a garment mid'Oraisa, but one is permitted to sit on it even mid'Rabanan. The Rabanan did not prohibit sitting on such material because it is uncommon ("Lo Shachi'ach").
(b) RASHI in Yoma (69a, DH Shari) writes that one is permitted to place Kil'ayim of a hard material on one's body ("Ha'ala'ah") even though one normally is prohibited mid'Oraisa from placing Kil'ayim on one's body. "Ha'ala'ah" is forbidden only when it is done in a manner similar to the way a garment is worn, for only in such a way does it give a person some form of pleasure (it provides warmth).
Rashi implies that wearing Kil'ayim ("Levishah") is always forbidden, even when the material is hard, because (as the TOSFOS RID here writes) when one wears an item he derives benefit not only from the warmth that it provides but from the protection that it affords or from the honor that it brings him. In the case of "Ha'ala'ah," however, the only benefit one derives from the cloth is the warmth.
(c) TOSFOS here and TOSFOS YESHANIM in Yoma (69a) explain in the name of RABEINU TAM that whenever an Isur d'Rabanan of Kil'ayim applies (such as in the case of lying down on a normal garment of Kil'ayim), the Rabanan permitted one to use the Kil'ayim if it is made of a hard material. In contrast, any form of Kil'ayim which is Asur mid'Oraisa remains Asur mid'Oraisa even when it is a hard material. Therefore, the Rabanan permitted one to sit on Kil'ayim (an act which normally is prohibited mid'Rabanan), or to wear a garment made from threads of wool and linen which were pressed but not woven (which is prohibited mid'Rabanan), if it is a hard material.
(d) The RA'AVAD in Tamid (27b) permits one only to lie on or sit on Kil'ayim of a hard material. He maintains that only "Hatza'ah" is permitted when the material is hard. Any other form of the prohibition of Kil'ayim d'Rabanan remains prohibited even when the material is hard (such as wearing a garment of pressed threads which were not woven). He says in the name of Rabeinu Efraim that the threads of a hard cloth do not have a tendency to wrap up around the person's body, and therefore the Gezeirah against lying on Kil'ayim does not apply to hard material.
(e) The RAMBAM (Hilchos Kil'ayim 10:13) rules that wearing Kil'ayim of a hard material is forbidden mid'Oraisa. One is permitted only to lie on or sit on hard Kil'ayim ("Hatza'ah") but not to wear it ("Levishah") or place it on top of his body ("Ha'ala'ah"), as the Ra'avad in Tamid rules.
Moreover, the allowance to lie on or sit on hard Kil'ayim applies only when the material does not touch the person's skin. According to the Rambam, one may not sit directly on top of the Kil'ayim (with no intervening material). (The Ra'avad in Tamid suggests that the reason why the Rambam prohibits sitting directly on hard Kil'ayim is because the Rambam maintains that "Ha'ala'ah" applies whenever the Kil'ayim is in direct contact with the person's skin, whether the garment is on the person or the person is on the garment. "Ha'ala'ah" is forbidden mid'Oraisa, and therefore it remains forbidden even when the Kil'ayim is a hard material.) (See also Insights to Yoma 69:3.)
2) HOW DOES AN ERUV TAVSHILIN PERMIT AN ISUR D'ORAISA
QUESTION: The Mishnah states that the Rabanan instituted the act of Eruv Tavshilin in order to permit cooking on Yom Tov for Shabbos. The prohibition to cook on Yom Tov for Shabbos, however, is a Torah prohibition, as Rabah states earlier (2b; "Hachanah d'Rabah"). How can the rabbinical enactment of Eruv Tavshilin remove the Isur d'Oraisa against preparing food on Yom Tov for Shabbos? (TOSFOS 2b, DH v'Hayah)
(a) TOSFOS answers that although the Torah forbids cooking on Yom Tov for Shabbos, the principle of "Ho'il" removes that prohibition. "Ho'il" ("since") states that since guests might arrive on Yom Tov, the potential host is permitted to cook for them on Yom Tov even if they do not end up coming. It is considered as though he is cooking for Yom Tov and not for Shabbos. (In fact, Rabah himself utilizes the principle of "Ho'il" in Pesachim (46b).) Even though the Isur d'Oraisa of cooking on Yom Tov for Shabbos does not apply because of "Ho'il," the Rabanan prohibited it lest one think that he is permitted to cook on Yom Tov for an ordinary weekday. The enactment of Eruv Tavshilin removes that prohibition.
However, according to Tosfos, since the allowance to cook on Yom Tov for Shabbos is because of "Ho'il," one should not be permitted to cook on Yom Tov for Shabbos near the end of the day on Yom Tov when there is not enough time for guests to arrive and to partake of the food. In such a case the Isur d'Oraisa will remain and an Eruv Tavshilin will not be able to permit it.
(b) TOSFOS here and in Eruvin (38a, in the name of the RITZBA) answers further that cooking a food that already exists is not called Hachanah and is not forbidden mid'Oraisa. It is called Hachanah only when a new product is created on Yom Tov that will be used on Shabbos (such as an egg that was laid on Yom Tov). Cooking a food that already exists is prohibited only mid'Rabanan, and thus the Eruv Tavshilin permits it.
(This is consistent with Rashi's interpretation of Hachanah (2b). Rashi repeatedly emphasizes that Hachanah prohibits an item that was prepared b'Yedei Shamayim on Yom Tov for Shabbos. If it already existed but was processed by man on Yom Tov for Shabbos, it is not prohibited because of Hachanah.)
3) HOW TO EXPERIENCE SIMCHAS YOM TOV
QUESTION: Rebbi Eliezer was upset with his Talmidim who left the Shi'ur early on Yom Tov to go and eat. He referred to the first group which left as those who have big vats set aside which they must eat. He said that the second group which left had barrels, the third group had jugs, the fourth had flasks, and the fifth had cups (that is, they had successively smaller vessels which hold smaller amounts of food). When the sixth group left, he said, "Those people are cursed!"
If Rebbi Eliezer was less upset with each group which left, as implied by the appellations which he ascribed to each one, then why did he express the most indignation at the last group and curse them?
(a) RASHI (DH Halalu) explains that aside from the Bitul Torah that the last group caused themselves, they were also guilty of slighting the honor of the Torah by leaving the Shi'ur. Until that point, there still remained a respectable number of Talmidim in the Shi'ur. After the sixth group left, however, the number of students left in the Shi'ur became noticeably small.
(b) The ARUCH (Erech "Pat") suggests a different approach. Rebbi Eliezer is the source of the opinion (quoted later in the Gemara) that Yom Tov is a day designated either exclusively for one's own personal pleasure or exclusively for Hash-m and for spiritual pursuits. The simple understanding of this statement is that one may choose what type of activities to pursue on Yom Tov and he is not required to split the day between the two pursuits, as Rebbi Yehoshua maintains. Rebbi Eliezer was upset with his Talmidim because they were students of the Torah and for them it was a far greater Mitzvah to spend Yom Tov immersed in learning Torah. To leave the Shi'ur in order to partake in the Yom Tov meal would constitute Bitul Torah for them because they were able to fulfill the Mitzvah of Simchas Yom Tov through learning Torah. They did not need to eat in order to experience Simchas Yom Tov.
The Aruch elucidates the opinion of Rebbi Eliezer. Rebbi Eliezer maintained that one must focus on one particular form of Simchas Yom Tov to the fullest extent possible. Therefore, one must either learn Torah all day or eat and drink all day. (That is, one should not decrease the size of his meal in order to be involved in spiritual pursuits such as learning Torah, and, similarly, one should not decrease the time he learns Torah in order to be involved in a Yom Tov meal. When he finishes his meal, or his studying, he certainly is permitted to involve himself in other pursuits.) One cannot dedicate the day to both pursuits, since he will not be able to do either one to its fullest extent.
When the first group of Talmidim left, Rebbi Eliezer commented that they must have had big vats ready and waiting for them. He meant that they were doing nothing wrong by leaving the Shi'ur early in order to partake in their Yom Tov meal. Those Talmidim chose not to spend the day learning Torah because they wanted to focus all of their energies on experiencing Simchas Yom Tov through involvement in the festive meal. As each successive group left, Rebbi Eliezer judged them favorably and assumed that each group had a certain amount to eat, and that they left the Shi'ur in order to utilize the remaining time to experience Simchas Yom Tov with the amount of food that they had.
In contrast, when the sixth group left, Rebbi Eliezer reasoned that they will not have sufficient time to eat a proper Se'udah for Yom Tov because it was so late already, and thus they will not experience Simchas Yom Tov through the meal. On the other hand, since they were leaving the Shi'ur early, they were losing the Simchas Yom Tov attained through total immersion in Torah study. Since they had neither the Simchas Yom Tov of eating nor the Simchas Yom Tov of learning Torah, Rebbi Eliezer said that they were cursed.