Halakhah su Levitico 27:33

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.)

To not sell the tithe of beasts, but rather that it be eaten in Jerusalem: To not sell the tithe of beasts in any way, but rather its owners - or whoever they want - eat it in Jerusalem. And regarding this is it stated here about the tithe of beasts (Leviticus 27:33), "it shall not be redeemed." And they said in Sifra, Bechukotai, Chapter 13:4, "With the tithe, it states, 'it shall not be redeemed' - it is not sold, neither alive nor slaughtered; neither unblemished nor blemished." And the expression of redemption is used here as an expression of sale, because redemption is similar to sale, since [redemption is when] a man gives value (money) and he purchases land.