Halakhah su Levitico 27:10

To not exchange consecrated things: To not exchange consecrated things - meaning to say one should not exchange a beast that has been consecrated for another beast afterwards, but it should rather be offered itself. And about this is it stated (Leviticus 27:10), "He shall not substitute nor exchange for it." And from when they exchanged it - meaning, that they said, "This instead of that"; "This in exchange for that"; or what is similar to these expressions, which is the essence of exchange (Temurah 26b) - there is liability for lashes in the thing, even though there is no act [involved] with it. [This is the case] even if there was somewhat of an error in the case. How is this? One who intends to say, "Behold this is in exchange for the burnt-offering that I have," but he says, "in exchange for the peace-offering that I have" - behold, this is an exchange and he is lashed; as nonetheless regarding the exchange it was volitional. But if his thought was that it was permissible to exchange, he is certainly not lashed. For one, it was inadvertent. And also, we only administer lashes with witnesses and a warning - and behold there is no warning [in such a case].

The commandment of the one who exchanges the beast of a sacrifice with another beast, such that both of them be consecrated: That the exchange be consecrated - meaning to say, that both will be consecrated if one exchanges the beast of a sacrifice with another beast, such that he said, "This one will be for a sacrifice in exchange for that one," as it is stated (Leviticus 27:10), "and it and its exchange will be consecrated." And this passage is a positive commandment - meaning that the Torah commanded us that the exchange be holy and that we practice holiness with both of them. And the proof that this is a positive commandment is their, may their memory be blessed, saying in Tractate Temurah 4b regarding the one who exchanges, "A positive commandment does not come and uproot two negative commandments." [This is] meaning to say that the prevention of exchange is repeated twice - as it is stated, "He shall not exchange nor substitute for it" - and the positive commandment of "and it and its exchange shall be" does not come and uproot these two negative commandments. Behold, what we wanted is elucidated, that it is a positive commandment.