1) USING THE "PARSHAS SOTAH" OF A SEFER TORAH
QUESTION: The Gemara relates that Rebbi Meir would put Kankantum into the ink he used for writing Sifrei Torah so that the text would be permanent and indelible. When Rebbi Yishmael (or, according to the second version, Rebbi Akiva) found out about Rebbi Meir's practice, he told Rebbi Meir to stop using Kankantum in his ink because the Torah says "u'Machah" (Bamidbar 5:23) in the Parshah of Sotah, which teaches that the Parshah of Sotah must be erasable.
Why is the requirement to erase the Parshah of Sotah related to the laws of the ink used to write a Sefer Torah?
(a) RASHI explains that Rebbi Yishmael told Rebbi Meir to stop using Kankantum in his ink only when he writes the Parshah of Sotah in the Sefer Torah. Rebbi Yishmael maintained that the Megilas Sotah does not have to be written "Lishmah," and thus one may use the Parshah of Sotah written in an actual Sefer Torah as the Megilas Sotah (to immerse in the Mei Sotah and erase the words).
According to Rashi's explanation, the reason why Kankantum may not be used in the writing of a Sefer Torah is unrelated to the validity of the Sefer Torah. The Sefer Torah is valid whether or not Kankantum is used in the ink. The only reason why Kankantum may not be used is so that the Parshah of Sotah written in the Sefer Torah may be used as the Megilas Sotah (see RITVA to Eruvin 13a).
Why must the Parshas Sotah of every Sefer Torah be written in a way that will make it valid for use to test a Sotah? The answer is that people assume that no Sofer who writes a Sefer Torah uses Kankantum (presumably so that they can erase and correct their mistakes). By using Kankantum in his ink, Rebbi Meir would cause the Kohen to err should the Kohen attempt to use the Parshas Sotah from Rebbi Meir's Sefer Torah as the Megilas Sotah. The Kohen would think that it was not written with Kankantum (and is erasable), when in fact it was written with Kankantum.
A number of questions may be asked on this explanation.
1. Why would a Kohen use the Parshas Sotah from Rebbi Meir's Sefer Torah? Even if Rebbi Meir did not use Kankantum, the Parshas Sotah must be written only after the Kohen was Mashbi'a the woman (as the Gemara earlier (17b) teaches). Rebbi Meir's Sefer Torah obviously was written before the Hashba'ah. (TOSFOS DH Amar)
2. The Gemara earlier (17b) teaches that the Megilas Sotah must be written during the day and not at night. If Kankantum may not be used because the Parshas Sotah in the Sefer Torah must be fit for use as the Megilas Sotah, must every Sefer Torah also be written only during the day? (See RASHASH.)
3. The verse says, "v'Kasav ha'Kohen" (ibid.), and teaches that the Kohen must write the Megilas Sotah. Everything the Torah instructs in Parshas Sotah is "Me'akev"; if any part of the procedure of the Mei Sotah is omitted, the entire procedure invalid. Indeed, the RAMBAM (Hilchos Sotah 4:9) rules that a Megilas Sotah written by a non-Kohen is invalid. Why, then, was the Parshas Sotah from the Sefer Torah which Rebbi Meir wrote valid for use as the Megilas Sotah? Rebbi Meir was not a Kohen. (See REBBI AKIVA EIGER in his notes to the Rambam in Hilchos Sotah 4:9, in the name of TESHUVOS MAHARI MI'BEIS LEVI #37; RASHASH.)
4. What difference does it make if a Kohen does not know that Rebbi Meir used Kankantum in his Sefer Torah? The Halachah is that the Kohen may give the water to the woman only after the ink is entirely erased in the water and no impression of ink remains on the parchment ("Ein Rishumo Nikar"). If Rebbi Meir used Kankantum in his ink, the Kohen will see for himself that the words on the parchment are not erased and he will not use it for the Megilas Sotah!
Perhaps the first three questions on Rashi's explanation may be answered as follows. Those who maintain that the Megilas Sotah may be taken from a Sefer Torah do not require that it be written "Lishmah," as Rashi here writes and as the Gemara concludes (20b). Although the verse says "v'Asah Lah" (Bamidbar 5:30) and implies that the procedure of the Megilas Sotah must be done "Lishmah," they understand that this verse refers only to the erasing (Mechikah) of the Megilas Sotah and not to its writing (Kesivah). Those who argue maintain that "v'Asah Lah" refers to the Kesivah as well as the Mechikah.
This dispute is similar to the Machlokes Tana'im with regard to the writing of a Get. Some Tana'im maintain that the Kesivah (writing) must be done "Lishmah," while others maintain that only the Chasimah (signing) must be done "Lishmah." According to the opinion that only the Chasimah must be done "Lishmah," not only does the Kesivah not have to be done "Lishmah" but none of the unique Halachos of Get apply to the writing of the Get.
Similarly, according to the opinion that requires that only the Mechikah of the Megilas Sotah be done "Lishmah," the way the Parshah is written cannot affect its validity. Consequently, not only does the writing of the Megilas Sotah not require "Lishmah," but the other laws of the writing of the Megilah also do not apply: it does not need to be written after the Hashba'ah, it may be written during the day or during the night, and it may be written by a Kohen or by a non-Kohen. (Although the verse states that it is a Mitzvah for the Kohen to write it, if a Kohen does not write it the Megilas Sotah nevertheless remains valid.)
Hence, Rebbi Yishmael -- who ruled that the writing of the Megilas Sotah does not need to be "Lishmah" -- indeed accepted a Parshas Sotah taken from a Sefer Torah written by Rebbi Meir as a valid Megilas Sotah, as long as it was written with erasable ink. (M. KORNFELD and D. Zupnik)
The answer to the fourth question may be as follows. Although the Kohen would not use the Megilas Sotah if he notices that its text does not become erased, it is possible that the Kohen will not look at the Megilas Sotah to verify that there is no impression left; he will assume that it was all erased and he will give the invalid Mei Sotah to the woman to drink.
Alternatively, Rebbi Yishmael was concerned not for the validity of the Megilas Sotah when he told Rebbi Meir not to use Kankantum in the writing of a Sefer Torah, but rather he was concerned for the honor of the Sefer Torah. Rebbi Yishmael maintained that it is not considered a disgrace to cut out or erase a part of the Sefer Torah to use for the Megilas Sotah, since the purpose of doing so is to bring peace between a husband and wife. However, if the Parshah will turn out to be an invalid Megilas Sotah (i.e. it was written with Kankantum), it certainly would be a disgrace to the Sefer Torah to cut out words and partially erase it for no purpose. That is why Rebbi Yishmael ruled that the Sofer must ensure that the Parshas Sotah in a Sefer Torah will be valid for use as a Megilas Sotah and may not be written with Kankantum. (M. KORNFELD)
Rashi explain the Gemara in this manner in order to answer the question which the Gemara asks on the Beraisa. The first Beraisa says that Rebbi Yishmael told Rebbi Meir not to use Kankantum because it is not valid for writing the Parshas Sotah. The second Beraisa says that Rebbi Meir told Rebbi Akiva that Rebbi Yishmael never told him not to use Kankantum. The Gemara presents this as a contradiction and leaves it unanswered ("Kashya"). However, the RASHBAM in Bava Basra (127a, DH Kashya) and RASHI in Sanhedrin (72a, DH Kashya) point out that the difference between a "Kashya" and a "Teyuvta" is that a "Kashya" can be answered (albeit with a forced answer). The way in which Rashi explains the Sugya here presents an answer to the "Kashya" of the Gemara, as follows.
When Rebbi Yishmael told Rebbi Meir not to use Kankantum, he meant that Rebbi Meir should not use Kankantum because the Parshas Sotah should be valid for use as a Megilas Sotah, and not because the Kankantum would invalidate the entire Sefer Torah. That is what Rebbi Meir meant when he told Rebbi Akiva that Rebbi Yishmael never stopped him from using it (i.e. because of the Kedushah of the Sefer Torah). Rebbi Akiva (when Rebbi Meir learned under him a second time, after he learned under Rebbi Yishmael), however, told him not to use the Kankantum because the Sefer Torah itself should not be written with Kankantum. (In fact, perhaps Rebbi Akiva prohibited the use of Kankantum not only for the Parshas Sotah section of the Sefer Torah but for any part of the Sefer Torah).
(b) TOSFOS here explains, like Rashi, that Rebbi Yishmael stopped Rebbi Meir from using Kankantum in the ink he used only for writing the Parshah of Sotah in the Sefer Torah. Tosfos explains that this is a requirement in the laws of writing a Sefer Torah and not in the laws of writing the Parshas Sotah, because in the times of Rebbi Meir (after the Churban) the Megilas Sotah was no longer in use.
The reason Kankantum may not be used in the writing of a Sefer Torah is that the Halachah that the Parshah of Sotah must be erasable ("u'Machah") applies to any Parshah of Sotah that is written -- whether it is written for the purpose of Mei Sotah or whether it is written as part of a Sefer Torah. (This is true only according to those who maintain that a Parshas Sotah from a Sefer Torah may be used as a Megilas Sotah in the Mei Sotah. According to those who maintain that a Parshas Sotah from a Sefer Torah may not be used for the Mei Sotah, when it is written as part of a Sefer Torah it does not have the title of a "Parshas Sotah" since it does not have the same use as a Megilas Sotah written for the Mei Sotah, and thus the requirement of "u'Machah" does not apply.)
(c) TOSFOS in Eruvin (13a, DH Chutz) explains that Rebbi Yishmael prohibits the writing of the entire Sefer Torah with Kankantum, and not only the Parshah of Sotah. This is either because Rebbi Yishmael maintains that there is a Gezeirah Shavah which compares the writing of a Sefer Torah to the writing of a Megilas Sotah, or because Rebbi Yishmael maintains that, mid'Rabanan, Kankantum may not be used for the entire Sefer Torah lest one mistakenly use it for the Parshah of Sotah.