Temurah, Chapter 1, Mishnah 6. Let us recall that this entire tractate revolves around a very small number of verses, the main ones being in Vayikra chapter 27, verses 9-10:
"Ve'im behemah asher yakrivu mimenah korban laHashem" - the subject is an animal that is a sacrifice, and the word "korban" is essential here.
"Lo yachalifenu velo yamir oso" - one may not exchange it and one may not substitute it. The wording is masculine, third person singular, which is unusual: the one who does this shall not exchange and shall not substitute.
"Ve'im hameir yamir behemah bivhemah" - and here the word "behemah" is essential, since it refers specifically to farm animals: cattle, goats and sheep.
"Vehayah hu usemuraso yihyeh kodesh" - both the original animal and its substitute become consecrated.
On the basis of these verses the Mishnah teaches several laws.
"Ha'ofos vehamenachos einan osin temurah":
A bird that was consecrated as a sacrifice - an olas ha'of or a chatas ha'of - even though it belongs to the category of kodshei kodashim, is not a "behemah," and the verse excludes it. Therefore, if a person attempts to substitute a bird for an existing consecrated olas ha'of or chatas ha'of, nothing takes effect and nothing at all has happened. The same applies to meal offerings: they too belong to kodshei kodashim, they can carry inherent sanctity, and they are brought as sacrifices - but they are not an animal. Therefore, if a person attempts to substitute a second meal offering for a first meal offering, even if he used the terms "in place of" or "substitute," his words accomplish nothing, "shelo ne'emar ela bivhemah" - for the verse explicitly limited this to an animal alone.
"Hatzibbur vehashutafin einan osin temurah":
A sacrifice purchased with communal funds, or a sacrifice that has partners - that is, that more than one person owns it - has no power to generate a substitute and to consecrate a second animal. "Shene'emar: lo yamir oso" - and from here we learn that an individual generates a substitute, but not the community and not partners.
And if you should ask: does the Torah not always speak in the singular, so why would it have occurred to us that the verse is speaking in the plural?
Indeed that is so, but here the wording is third person masculine singular, and that is unusual. Ordinarily, when the Torah commands to do or not to do something, it uses the second person: "lo samir." What then is "lo yamir"? He shall not substitute - and from here we learn that the subject is "he," in the singular and not the plural. And you should remember that at the beginning of the tractate we learned that a substitution is made either by a male or by a female, that is, by a man or a woman who owns the sacrifice, but that was a novel teaching, since from that very same word "yamir" one would understand men alone, and it was the extra vav that came to include women. Here, by contrast, the inference is from the unusual singular form, which is in the third person rather than the second person. In Hebrew, the second person is called nochach and the third person is called nistar. This is nistar, and from here we learn that the subject is specifically individuals, and not multiple owners or a community that owns the sacrifice.
"Korbanos bedek habayis ein osin temurah":
Similarly, an animal that was consecrated not with the sanctity of the altar, to be offered upon the altar, but only with the sanctity of bedek habayis - that is, monetary sanctity, where its value was set aside and not its body - also cannot generate a substitute. Here is an example: a person comes to the Beis Hamikdash and sees that one of the basins is cracked. He says to himself: a new basin must be purchased for the Beis Hamikdash, and I have no money, only a single cow - I hereby consecrate this cow to the Beis Hamikdash, so that they will have money to repair the basin.
With this consecration he is not consecrating the cow with inherent sanctity to be offered on the altar; rather, he is giving its value to bedek habayis for the upkeep of the Mikdash, and the Beis Hamikdash will sell it at public auction and use the proceeds to purchase a new basin. It turns out that this animal was consecrated with the sanctity of bedek habayis alone - monetary sanctity, an external sanctity in which the value is consecrated and not the object itself. Therefore, if a person says that he is substituting it with another animal, using the language of substitution or the language of exchange, it accomplishes nothing, and the sanctity does not transfer. Of course, he may redeem it or sell it and transfer the sanctity of its value onto the money, but that is not our concern here. The rule is that sanctity cannot be transferred by way of substitution when the animal that is the source of the sanctity carries only monetary sanctity - the sanctity of bedek habayis - and not inherent sanctity to be offered upon the altar.
And where do we know this from? The verse refers to the animal as a "korban," and our Tanna understands that the term "korban" does not apply to a cow that was consecrated only for the needs of the Temple upkeep and not to be offered on the altar, and that is enough.
Now you might ask: the Mishnah itself uses the phrase "korb'nos bedek habayis," which implies that the word "korban" does apply to animals of Temple upkeep. There are two ways to answer. It is possible that the language here is being used loosely, and indeed it seems that Rabbi Shimon later on holds that the word "korban" can apply even to such a thing. And it is possible that the Rishonim had a different text: the Bartenura, and Rashi like him, read "kodshei bedek habayis" instead of "korb'nos bedek habayis," and according to this approach the word "korban" does not appear in our Mishnah at all. In any case, the derivation turns on the word "korban": a korban is fit for temurah, and this is not a korban.
The view of Rabbi Shimon:
Rabbi Shimon comes to disagree, but his disagreement concerns the source of the laws and not the laws themselves. He agrees with the rulings that were stated, only that in his view they must be derived from other sources, since the word "korban" can apply even to an animal that was consecrated for Temple upkeep. So where is the other source? As we mentioned in the introduction to the tractate, and at the end of tractate Bechoros, the verses in chapter 27 forbid temurah twice and establish that the substitution is forbidden yet nevertheless takes effect: the basic verses that we read in verse 10, and again at the end of the chapter in the context of the animal tithe.
And these are the verses regarding the animal tithe: "And every tithe of the herd and the flock, whatever passes under the rod, the tenth shall be holy to Hashem" - the tithed animals, whether of the herd or of the flock, when they pass under the rod at the door of the pen, the tenth of them becomes consecrated to Hashem. And afterwards, in verse 33: "He shall not distinguish between good and bad, and he shall not substitute for it" - a person should not say: the tenth one that came out is a weak animal, and perhaps it is blemished, and I would like to exchange it. He should not do so and should not substitute for it. "And if he does substitute for it, then it and its substitute shall be holy" - and if he does substitute, the substitution takes effect and both become consecrated, the first and the second. "It shall not be redeemed" - and neither of them can be redeemed.
And the question that Rabbi Shimon focuses on is this: why did the verse need to say this? It was already stated in the chapter in a general way that one may not substitute or exchange offerings, and that would include the animal tithe, which is also one of the offerings. So why does the verse repeat itself? To this Rabbi Shimon says that this is a classic example of the Torah singling out a specific case that was not needed, in order to teach that the laws of temurah apply to offerings that resemble the animal tithe.
And in the words of the Mishnah: "Amar Rabbi Shimon: vahalo hama'aser bichlal hayah, velamah yatza?" - the tithe, meaning the animal called ma'aser, was already included in the general prohibition of temurah stated earlier in the chapter, so why did the Torah single it out again? Rather, "l'hakish eilav" - to draw a comparison to it:
"Mah ma'aser korban yachid" - the animal tithe never comes from anyone other than a private individual, and not even in partnership. This is learned from the word "lecha," as we learned at the end of the last chapter of tractate Bechoros. And from here: "yatz'u korb'nos tzibbur" - communal offerings are excluded, and included in this is even an offering that is jointly owned.
"Mah ma'aser korban mizbe'ach" - the tithe is from the animals that go up on the altar, and it is not like items consecrated for Temple upkeep. And from here: "yatz'u korb'nos bedek habayis" - offerings of Temple upkeep are excluded.
It emerges that Rabbi Shimon is saying: I agree with the laws themselves, only that their source is different.
But this turns our attention back to the Tanna Kamma: according to his view, why did the Torah repeat the laws of temurah and forbid them regarding the animal tithe, something that was not needed? The answer lies in what we learned at the end of tractate Bechoros, that there is a way in which a substitution is made with the tithe by mistake: one who calls the ninth animal that came out of the pen "tenth," or who did not call the tenth "tenth" but called the eleventh by that name - in which case the ninth and the eleventh also receive a sort of status of tithe, and they are treated with sanctity and with some of the prohibitions of the tithe, as detailed there at the end of Bechoros. The point is that the additional repetition comes to teach us this further law, that the ninth or the eleventh that came out of the pen become substituted and receive a certain level of sanctity like the tithe.