Kommentar zu Wajikra 27:10

טוב ברע [HE SHALL NEITHER CHANGE IT NOR EXCHANGE IT] A GOOD FOR A BAD — i. e. he shall not give in exchange a perfect animal of a non-sacred character for one devoted to the Sanctuary but having some blemish (cf. Rashi on Temurah 9a on ‎‎‎מתני' טוב ברע),

He shall not substitute it, nor exchange it: This is the generalization. And then it explained [its] details - that he should not exchange it good with bad, nor bad with good. But according to the author of the cantillation marks, it appears that exchange (temurah) [means] of good with bad, and substitution (chiluf) is of bad with good. And there is support for this: "We shall substitute cedars" (Isaiah 9:9); "Those that fear the Lord shall substitute (renew) strength" (Isaiah 40:31); "And they exchanged their glory for the edifice of a bull"...

לא יחליפנו ולא ימיר אותו טוב ברע או רע בטוב, “he shall not exchange it or substitute it, good for bad or bad for good.” According to Maimonides Hilchot Temurah 4,13 the reason for this legislation is that the Torah explored the psyche of the donor down to its ultimate depth. At the core of a human being, even the finest, there may still be lying in wait for him the evil urge. Even though the person in question made these vows entirely voluntarily, not in response to any pressure, he may yet at some time or other rue having made such a vow. His first attempt at getting out of his obligation would be to exchange the animal designated for the altar with an inferior one. Seeing that the animal he sanctified was suitable as an offering, the sanctity becomes part of its body and it cannot be exchanged. This is why the Torah stated flat out that such an animal as described in our verse לא יחליפנו, cannot be traded at all. If the Torah were to permit the donor to upgrade the animal in question, it would not be long before people would abuse such a rule and they would start downgrading it for an inferior beast. If the donor violated this legislation by substituting, not only would he not gain thereby but he is punished by the Torah which states that the substitute will also become sanctified thus depriving the donor of both animals.
והיה הוא ותמורתו קדש, “and both it (the original) and its substitute will remain sacred.” Keeping in mind the reason Maimonides advanced for this legislation, we can now understand why the Torah demanded that if someone who had sanctified his house for the Temple Treasury [a lesser degree of sanctity as the house could not be offered as an offering on the altar, Ed.] and he wants to redeem it from the Temple treasurer offering to pay for it, must add 25% as a premium to its value. The Torah’s reading of our minds allows for the fact that we may change our minds. In order to remind us that such a change of mind is not appreciated, the Torah imposes a price on that privilege of a person to change his mind (compare Nachmanides).

... 37... And it appears to require more explanation: The word, substitution (chalifin), is different than the word, exchange (temurah), in that substitution is a change in the body of the thing, such that another comes in its place, as in "and change your clothes" (Genesis 35:1); whereas exchange is only an emotional change, as in "And they exchanged their glory with the edifice of a bull" (Isaiah 40:31). And the matter is understood.

An unblemished one for one which has a blemish. I.e., he may not give an undedicated unblemished animal in place of an already dedicated one which has a blemish. You might ask: How does Rashi know this? Perhaps the verse means according to its plain meaning, a fat one for a thin one? The answer is: We find elsewhere regarding sanctified animals that it is written רעand “blemish” is written next to it, indicating that wherever it says ‘bad’ regarding sanctified animals, it means a blemish. Because it is written in parshas Re’ey (Devarim 15:21), “And if it has a blemish, if it is crippled or blind, or has any severe (רע) blemish.”

טוב ברע או רע בטוב, “(substituting) good for inferior, or inferior for superior. The reason why the Torah had to write both alternatives is because the owner does so as he is not sure which is superior and which is inferior. In the case of the animals proving to be diseased and therefore at least one of them being disqualified as an offering, the donor did not know which of the sicknesses is the more serious one. (B’chor shor)

He shall not exchange it. Usually חליפה connotes exchange from poor quality to high, as in (Yeshayahu 9:9): “Sycamores have been cut down, and we will exchange them with cedars,” and (ibid. 40:31): “But those who put their hope in Adonoy shall renew strength.” However, the matter of exchanging a sacrifice is the opposite, because one usually exchanges the fine one for one of poor quality, as it says (Hoshea 4:7): “I will exchange their honor for shame”.

‎‎‎או רע בטוב‎ OR A BAD FOR A GOOD — It follows à fortiori that he must not give in exchange a perfect animal for another perfect one, or one with a blemish for another with a blemish (Temurah 9a).

And certainly (כל שכן) [the exchange of] good for good or bad for bad. You might ask: Why is this a כל שכן?” Perhaps one may only not change a bad undedicated [animal] for a good dedicated one, but if they are both good, this כל שכן does not indicate that it is forbidden? Also, why does the Torah need to write “a good one for a worse one”? This would be a כל שכן as even a bad one for a good one is forbidden? Also, why does Rashi explain “certainly good for good” when discussing “a bad one for a good one”? He should have explained this while discussing “a good one for a bad one”! The answer is: He means as follows. The verse certainly has to write “or a bad one for a good one” because of the end of the verse where it says, “If he did exchange, etc., then both it and its replacement shall be sacred.” This indicates that after the act they are both sacred. Therefore the Torah needs to write “a bad one for a better one” to include that even if one gives a bad one in exchange for something better that was dedicated, where one may have thought it does not become sanctified at all, the verse lets us know that if one made such an exchange it is holy, since the end of the verse refers to both cases. And now that even a blemished one exchanged for an unblemished one, the blemished one becomes sacred, so then exchanging an unblemished one for an unblemished one, will certainly become sacred since both are good. You might ask: Why does Rashi [also] mention “bad for bad”? The answer is that you might have said this only works if one exchanges good for good because the sanctity of the good one has the power to fall on its exchange. However, if one exchanged bad for bad you might have thought that the sanctity of the blemished animal does not have the power to fall [on its exchange]. So Rashi tells us [that it does], because it is also written “a good one for a bad one.” Analyze this. See Re’m who discusses this at length, asking many questions.

That is that He commanded us that the substitute [of a consecrated item] be consecrated. And in the explanation in Tractate Temurah (Temurah 4b), they said that His saying, "he shall not substitute for it," is a negative commandment that is rectified by a positive commandment. And it is also said there - in order to give a reason for the one who substitutes to get lashes, even though it is a negative commandment that is rectified by a positive commandment - and they said, "A positive commandment should not come and uproot two negative commandments." That is to say, this prohibition of substitution has been repeated twice - "He may not exchange or substitute it" (Leviticus 27:10) - but [only] one positive commandment appears; and that is, "it and its substitute shall both be holy" (Leviticus 27:33). Behold what we have wanted to explain has been explained. And the laws of this commandment have already been explained in Temurah - meaning when it stands and when it does not stand and what its law is. (See Bechukotai; Mishneh Torah, Substitution 1.)