OPINIONS: The Gemara (12b) quotes the Mishnah in Ohalos (17:2) in which Rebbi Eliezer states that a Beis ha'Peras can make another Beis ha'Peras.
There are various explanations as to the meaning of Rebbi Eliezer's statement.
(a) RASHI (end of 12b, DH Rebbi Eliezer) explains that when a Beis ha'Peras is plowed along with its adjoining fields, the fields on all four sides become a Beis ha'Peras.
(b) TOSFOS (DH Shalosh) questions Rashi's explanation. In a case in which the owner of the field plowed the field in only one direction, why should the adjacent fields on all four sides become a Beis ha'Peras? (That is, if he plowed from north to south, then the fields to the east and west should not become a Beis ha'Peras, because the plowing never brought earth and bones to those sides.)
Tosfos therefore explains that when Rebbi Eliezer says that one Beis ha'Peras can make another Beis ha'Peras, he means that if the earth of a Beis ha'Peras is plowed into its adjacent field on one side, then that adjacent field becomes a Beis ha'Peras. If the earth of that second Beis ha'Peras is then plowed into another adjacent field, then that field becomes a third Beis ha'Peras, and so on.
Perhaps Rashi does not give this explanation because he understands that the Gemara is discussing a situation in which the direction the field was plowed (east-west or north-south) is not known. The Chachamim maintain that we assume it was plowed the way fields in that area normally are plowed. Rebbi Eliezer maintains that each of the four surrounding fields becomes a Beis ha'Peras, because of the possibility that the field with the bones was plowed in a different manner than the normal manner of plowing.
OPINIONS: The Mishnah quotes the Tana Kama who says that only an individual can make a Temurah with his Korban; the public (Tzibur) or partners cannot make a Temurah with a public Korban or with a jointly-owned Korban. RASHI (13b, DH Rebbi) explains that this is derived from the fact that the verses always discuss the Halachos of Temurah in the singular tense.
The Mishnah quotes Rebbi Shimon who derives from the fact that the verse repeats the law of Temurah when it discusses the laws of Ma'aser Behemah that Temurah can be done only with a Korban similar to that of Ma'aser Behemah. Ma'aser Behemah can be only the Korban of an individual, and it must be an animal that can be offered on the Mizbe'ach. This excludes a publicly-owned animal, and any animal that is Hekdesh Bedek ha'Bayis.
Do the Tana Kama and Rebbi Shimon argue only about the source for this Halachah, or is there some practical difference between them?
(a) The YAD BINYAMIN suggests a practical difference between the Tana Kama and Rebbi Shimon. The Tana Kama focuses on the fact that only an individual can make a Temurah. If an individual gives permission for the public to make a Temurah with his private Korban, then it seems that it would be invalid, since the Torah teaches only that an individual can make a Temurah. According to Rebbi Shimon, however, perhaps the Temurah would take effect in such a case. Rebbi Shimon's source does not discuss who makes the Temurah, but rather on what type of Korban it can be made. According to Rebbi Shimon, the Torah teaches that Temurah cannot be made with a public Korban. Accordingly, he might maintain that the public can make a Temurah with a privately-owned Korban. (A similar, practical distinction would apply in the opposite case, in which the public gives permission to an individual to make a Temurah with its Korban. According to the Tana Kama, the Temurah is valid, because it is an individual making the Temurah, while according to Rebbi Shimon, it is not valid, since the Korban is owned by the public.)
(b) The TOSFOS YOM TOV asserts that there is no practical difference between the Tana Kama and Rebbi Shimon. He says that when the verse excludes the public from the law of Temurah, it excludes both the public from making a Temurah, and a public Korban from having Temurah made with it. The Yad Binyamin points out that the Tosfos Yom Tov infers this from the words of the Tana Kama. When the Tana Kama says that only an individual can make Temurah since the verses discuss Temurah only in the singular tense, the Tana Kama understands that the verse is saying that Temurah can be made only by an individual, and it can be made only to his private Korban. Similarly, when Rebbi Shimon says that the prototypical Temurah is the animal used for Ma'aser Behemah, he means that not only must the Korban belong to an individual (and not to the Tzibur or to partners), but that Temurah itself can be made only by an individual. (A similar opinion is expressed by the RASHASH.) (Y. MONTROSE)


OPINIONS: Rebbi maintains that without a source in the Torah to teach that Temurah applies to a Korban of Ma'aser Behemah, one would have thought that Temurah does not apply to such a Korban. The Gemara asks why would one have thought that Temurah does not apply to Ma'aser Behemah? If one can make a Temurah with all other private Korbanos, why should one not be able to make Temurah with a Korban of Ma'aser Behemah?
Rav Huna brei d'Rav Yehoshua answers that the reason why one would have thought that Temurah does not apply to Ma'aser Behemah is the rule of "Davar she'Hayah bi'Chelal v'Yatza Lidon b'Davar he'Chadash, Ein Bo Ela Chidusho." This rule applies when an action or object was included in a general category of Halachah and was singled out in another verse in order to teach a new Halachah that applies to it, and that new Halachah contradicts the general rule of the Klal. This rule teaches that the new Halachah applies only to the specific action or object, and not to the general category (unless a verse specifically states otherwise). In the case of Ma'aser Behemah, the Torah teaches a novel law that Ma'aser Behemah takes effect even in error. If the tenth animal was not called "tenth" but the animal next to the tenth animal was called "tenth," then both it and the actual tenth become consecrated. The fact that the Torah teaches this new law with regard to Ma'aser Behemah indicates that the regular law of Temurah does not apply.
What is the definition of a "Davar Chadash," and when does the rule of "Davar she'Hayah bi'Chelel v'Yatza Lidon b'Davar he'Chadash" apply?
(a) The Gemara in Yevamos (7a) applies this rule to an Asham Metzora. The Gemara says that had the verse not taught that the laws of Zerikah and Haktaras Eimurin apply to an Asham Metzora, one would have thought that those laws do not apply to an Asham Metzora. Why would one have thought that an Asham Metzora differs from all other Korbanos? The Gemara explains that one would have thought that an Asham Metzora differs because the Torah teaches a new law with regard to an Asham Metzora: some of its blood is sprinkled on the big toe and thumb of the Metzora. This is a Davar Chadash.
TOSFOS there (DH l'Fi) asks that the Gemara should ask the same question with regard to a Chatas Metzora. The Torah teaches that Nesachim are brought with the Chatas Metzora, unlike any other Korban Chatas. Accordingly, one might assume that it, too, does not have Zerikah and Haktaras Eimurin! Tosfos answers that the rule of Davar Chadash applies only when the new law contradicts a pre-existing law. For example, without the Torah's command to sprinkle some of the blood of the Asham Metzora on the big toe and thumb of the Metzora, the law would have been that all of the blood is used for Zerikah on the Mizbe'ach. Since the new Halachah of sprinkling some of the blood on the Metzora's body contradicts the pre-existing Halachah (of using all of the blood for Zerikah), it is called a "Davar Chadash." In contrast, the fact that Nesachim are brought with a Chatas Metzora contradicts no other requirement of a Korban Chatas; it is merely an added requirement to bring Nesachim. Therefore, that law is not called a "Davar Chadash." This is also the explanation of RABEINU YAKOV of Orleans, quoted by Tosfos in Zevachim (49a, DH l'Fi she'Yatza).
The MELECHES CHOSHEV here has difficulty with the words of Tosfos in Yevamos. According to Tosfos' definition of "Davar Chadash," how does this concept apply to Ma'aser Behemah? The rule of Ma'aser Behemah is specific to the counting of Ma'aser Behemah. It does not interfere with any known rules of Korbanos, and yet the Gemara here invokes the rule of Davar Chadash! How does Tosfos explain the Gemara's application of Davar Chadash to Ma'aser Behemah?
(b) The BIRKAS HA'ZEVACH in Zevachim also asks this question on Tosfos. He points out that the view of Tosfos is not the position of the Toras Kohanim and Sifri, both of which are quoted by RASHI (see, for example, Zevachim 57a, DH Hachi Garsinan). They specifically state that the Korban Todah has a Davar Chadash, since an integral part of the Korban is the bringing of the Lachmei Todah, something that no other Korban has. According to Tosfos, this would not constitute a Davar Chadash, since it is merely an additional requirement, and not one that contradicts any other law of Korbanos. The Birkas ha'Zevach leaves this question on Tosfos unresolved.
The TZON KODASHIM in Zevachim (49a) answers the question on Tosfos. He explains that Tosfos agrees with the Toras Kohanim's position that an additional Halachah, like the Lachmei Todah of a Korban Todah, is called a "Davar Chadash." Why, then, does Tosfos say that the Nesachim of a Chatas Metzora is not considered a Davar Chadash? The Tzon Kodashim answers that a Halachah is considered a Davar Chadash only when it contradicts a general rule, but not when it contradicts a specific rule. The fact that a Chatas Metzora requires Nesachim does not make it a Davar Chadash, because most Korbanos (other than a Korban Chatas) require Nesachim. Accordingly, the fact that a Chatas Metzora is the only Chatas that requires Nesachim does not make it a Davar Chadash. In contrast, the Korban Todah requires that loaves be brought with it, unlike all other Korbanos, and thus the Korban Todah is considered a Davar Chadash. (Y. MONTROSE)