356. You Got Your Asham in My Shelamim!: The prohibition against altering a sacrifice’s type

Not only may one not exchange a sanctified animal for a different animal, one may not change the type of offering for which an animal has been consecrated. Our verse specifically prohibits consecrating a firstborn animal as a sacrifice but it is equally true when it comes to changing a guilt offering to a thanksgiving offering or any other sort of switch.

The reason for this mitzvah is similar to that of Mitzvah #352: we are supposed to take the Temple service seriously. We are not supposed to play fast and loose with consecrated animals, altering their status from one offering to another. Similar to this, if dedicated money is earmarked for the upkeep of the Sanctuary of the Temple, it may not be used to maintain the altar, or any other such substitution.

This mitzvah applies to both men and women in all times and places, though we should avoid consecrating things at a time when the Temple is not standing. If someone did consecrate an animal, it would be prohibited to change its designation. In the Talmud, it is discussed in tractate Arachin on page 29a. It is codified in the Mishneh Torah in the fourth chapter of Hilchos Temurah and is #107 of the 365 negative mitzvos in the Rambam’s Sefer HaMitzvos. This mitzvah is not listed in the Sefer HaMitzvos HaKatzar of the Chofetz Chaim.