1) THE "TUM'AH" OF OIL, HONEY, AND WINE
OPINIONS: The Gemara cites the Mishnah in Taharos (3:2) which mentions the types of liquids that "always" ("l'Olam") become Tamei with Rishon l'Tum'ah. Rebbi Meir says that oil always becomes a Rishon l'Tum'ah. The Chachamim say that even honey always becomes a Rishon, and Rebbi Shimon Shezuri says that even wine always becomes a Rishon.
The Gemara asks that the wording of Rebbi Shimon Shezuri ("even wine" becomes a Rishon) implies that the Chachamim argue and maintain that wine does not always become a Rishon. This cannot be so, however, because everyone agrees that wine certainly is a type of liquid that becomes Tamei. The Gemara answers that Rebbi Shimon Shezuri did not say "even wine," but rather he said that "wine" becomes a Rishon. This implies that it is not the Chachamim who argue with Rebbi Shimon Shezuri, but Rebbi Shimon Shezuri argues with Rebbi Meir and with the Chachamim and maintains that only wine becomes a Rishon, and not oil or honey.
When the Mishnah says that these things "always" become Tamei as a Rishon l'Tum'ah, what does it mean?
(a) RASHI (DH Shemen) explains that the Mishnah is teaching that these liquids are considered "Mashkeh" such that they become Tamei with Rishon l'Tum'ah regardless of what level of Tum'ah touches them. They become a Rishon whether they are touched by an Av ha'Tum'ah, Rishon l'Tum'ah, or by a Sheni l'Tum'ah. (An ordinary food item becomes a Sheni only when touched by a Rishon, or (if it is Terumah or Kodshim) it becomes a Shelishi when touched by a Sheni.) This is because of a Gezeirah d'Rabanan that any level of Tum'ah that causes Terumah to become Pasul causes a liquid to become a Rishon l'Tum'ah.
(b) TOSFOS (DH Eima) questions Rashi's explanation. The Gemara concludes that Rebbi Shimon Shezuri argues with Rebbi Meir and the Chachamim and maintains that neither oil nor honey becomes a Rishon l'Tum'ah when touched by another Rishon or a Sheni. According to Rashi's explanation, this means that Rebbi Shimon Shezuri maintains that oil is not considered a Mashkeh. However, there are numerous Mishnayos and Sugyos that clearly state that oil is a Mashkeh.
Tosfos therefore gives a different explanation. Tosfos says that the word "always" ("l'Olam") is teaching that even when the oil congeals, it remains Tamei with Tum'as Mashkin, and it remains a Rishon l'Tum'ah. This is in contrast to the first part of the Mishnah in Taharos which mentions various other types of liquids and says that "when they are completely liquid, they are a Rishon l'Tum'ah, but when they coagulate, they are only a Sheni l'Tum'ah." That is, when they solidify they are considered a solid food item that touched a Mashkeh, and they are only a Sheni l'Tum'ah. Indeed, in the next part of the Mishnah (which the Gemara here quotes), Rebbi Meir says that oil retains its status as a liquid even when it becomes solid. (The VILNA GA'ON in SHENOS ELIYAHU explains that this is because oil remains moist even when it congeals.)
The RA'AVAD (Hilchos Tum'as Ochlin 1:19) learns like Tosfos and explains that the word "l'Olam" implies that even when the oil solidifies, it is considered a liquid with regard to Tum'ah. Based on this Mishnah, he rejects the ruling of the RAMBAM who says that congealed oil does not become Tamei at all.
(c) The BIRKAS HA'ZEVACH explains that the RAMBAM has a different understanding of the word "l'Olam" in the Mishnah in Taharos. The Rambam (Hilchos Tum'as Ochlin 1:19) rules, as mentioned above, that oil that congealed does not become Tamei at all. However, elsewhere (Hilchos Tum'as Ochlin 9:1) the Rambam rules that if oil became Tamei while it was a liquid and then it congealed into a solid, and then it became a liquid again, it returns to its original state of Tum'ah. This is the meaning of the word "l'Olam" here; the liquid oil remains a Rishon l'Tum'ah even when it congealed after it had become Tamei and has now become a liquid again. This is in contrast to the liquids mentioned in the first case of the Mishnah, which, once they congeal, their Tum'as Mashkin does not return even when they become liquids again. (Only if, during the melting process, a k'Beitzah of the congealed liquid touches the melted liquid does the melted liquid become Tamei, because it touched the Tum'as Ochlin of the congealed liquid. It does not retain the original Tum'as Mashkin, as oil does.)
According to the Rambam, the reason for the difference between oil and other types of liquids that congeal is that oil that congeals remains moist (as the Shenos Eliyahu writes). This seems to be the intention of the Rambam himself in Perush ha'Mishnayos in Taharos when he says, "... because the congealed [oil] does not actually become congealed, and it is considered a liquid even when it seems to have solidified."
However, if congealed oil is not considered a real solid, then why does congealed oil itself not become Tamei with Tum'as Mashkin? The answer is that a person cannot eat or drink congealed oil, and thus the Tum'as Mashkin departs from it and returns only when it becomes a liquid again. This is in contrast to other liquids which solidify, which are considered solids in their congealed state such that their Tum'as Mashkin departs entirely. Those other liquids become fit for consumption when they congeal, and thus they have the status of solid food items and can become Tamei with Tum'as Ochlin (as a Sheni l'Tum'ah).
(The RASH in Taharos understands that Tosfos agrees with the explanation of the Rambam.) (Mordechai Zvi Dicker)
2) HALACHAH: REPAIRING A TEAR IN A SEFER TORAH
QUESTION: The Gemara says that if the parchment of a Sefer Torah tears, it must be sewn with "Gidin," strings made of sinews, and not with "Geradin," leftover threads from a cloth garment.
The REMA (YD 280:1) writes, "Some say that we may sew them with silk strings, and this is the practice today. However, the main law is to sew them with Gidin if possible."
The BEIS YOSEF and the VILNA GA'ON question the Rema's statement from the Gemara here that says clearly that a tear must be sewn with Gidin. Why does the Rema say that one may repair the tear with silk threads?
ANSWER: The ARUCH HA'SHULCHAN answers that although the Gemara says that a tear must be sewn with Gidin, it also says that a tear must not be sewn with Geradin. If, when the Gemara says that a tear must be sewn with Gidin, it means that only Gidin is permitted and nothing else, then why does the Gemara need to add that a tear should not be sewn with Geradin?
It must be that the Gemara does not mean that one must sew a tear only with Gidin. Rather, the Gemara means that one must sew a tear with a strong material, like Gidin, and not with a weak material, like Geradin, that will tear easily. Silk is very strong, and therefore some authorities, such as the ROSH, permit its use for the repair of a tear in the parchment of a Sefer Torah.
However, the Rosh's ruling is problematic for a different reason. A Halachah l'Moshe mi'Sinai requires that the separate folios of parchment of a Sefer Torah be tied together only with Gidin, sinews of a Kosher animal. The Gemara in Makos (11a) states that if the folios of a Sefer Torah are sewn with anything other than Gidin, the Sefer Torah is Pasul. Why, then, does the Rosh permit sewing a tear in the Sefer Torah with silk?
1. The ARUCH HA'SHULCHAN answers that the Halachah l'Moshe mi'Sinai that requires that a Sefer Torah be sewn with Gidin refers to an absolutely necessary, indispensable stitching. A Sefer Torah cannot be written on a single folio of parchment; it must be comprised of many folios that are attached to each other by sewing. This indispensable sewing must be done with Gidin.
In contrast, the Gemara here discusses stitching which is not part of the regular procedure of making a Sefer Torah. The parchment tore, and it must be repaired in order for the Sefer Torah to be whole and usable. The Halachah l'Moshe mi'Sinai does not give any guidelines for how to sew such a tear.
However, according to this answer, one should be permitted to sew two of the original folios of parchment together with silk when making the Sefer Torah. It is not necessary that every single folio of parchment be sewn to the next with Gidin, since instead of using two folios sewn together, one could use one large folio in their place.
The answer to this question may be inferred from the words of the TESHUVOS HA'ROSH (quoted by the Aruch ha'Shulchan). The Rosh there says that when the sewing is done "to fix the parchment, it may be done in any way." That is, when sewing together two separate pieces of parchment in order to attach them to make a Sefer Torah, the Torah requires that the sewing be done with Gidin. This is because sewing together two separate pieces of parchment does not make them a single piece of parchment, but rather the attachment makes the Sefer Torah into a whole Sefer. A whole Sefer must be formed only with Gidin.
In the case of a piece of parchment that tore, sewing together the torn part restores the unity of the parchment. It is not done to bind together different pieces to make a Sefer; it is done "to fix the [one piece of] the parchment" and so that "it may be done in any way." (Mordechai Zvi Dicker)