הזהירנו מהמיר קדשים. והוא אמרו לא יחליפנו ולא ימיר, וכבר באה האזהרה מיוחדת במעשר, והסבה מה שזכרו בספרי והוא אמרם מעשר בכלל היה ולמה יצא להקיש אליו מה מעשר קדשי מזבח ואין תמורתו מותרת אף כל קדשים אין תמורתן מותרת, והוא אמרו ולא ימיר, ואמרו לא יחליפנו אמנם הוא בקדשי מזבח לבד, והממיר לוקה. וכבר התבארו משפטי מצוה זו בתמורה. (אם בחקותי, הלכות תמורה פ"א): He prohibited us from substituting consecrated animals. And that is His saying, "One may not exchange nor substitute for it" (Leviticus 27:10). And the prohibition already appeared specifically about the [animal] tithe. And the reason is that which they mentioned in the [Sifra] (Sifra, Bechukotai, Chapter 9:4): And that is their saying, "The tithe was in the category [of all consecrated animals]. Why, then, was it singled out? To make a comparison to it: Just as the tithe is consecrated animals that go on the altar and its substitution is not permitted; so too, is the substitution of all consecrated animals that go on the altar not permitted." And that is His saying, "nor substitute for it," and His saying, "One may not exchange" - however that is only with consecrated animals that go on the altar. And one who substitutes [it] is lashed. And the regulations of this commandment have already been explained in Temurah. (See Parashat Bechukotai; Mishneh Torah, Substitution 1.)