פירוש על ויקרא 7:1

קדש קדשים הוא [THIS THE LAW OF THE GUILT OFFERING] IT IS MOST HOLY — “It is most holy”; it may be offered, but an animal that is exchanged for it (cf. Leviticus 27:34) may not be offered (Sifra, Tzav, Section 5 2).

But its exchange is not. Meaning: The exchanged animal itself is not sacrificed, nevertheless, it becomes holy and does not go out to become non-sacred. It is left to graze until it develops a blemish. Then, it is sold and its value is used to buy a voluntary offering.

That is that He commanded us with the process of the guilt-offering sacrifice - according to the description that is mentioned - with His saying, "And this is the law of the guilt-offering" (Leviticus 7:1). And Scripture explained how it is offered, what is burnt from it and what is to be eaten. (See Parashat Tzav; Mishneh Torah, Sacrificial Procedure 9.)