The Torah is clear that when someone attempts to switch the sanctity from an animal that is intended to be a sacrifice onto a different animal, both animals will become sanctified. This action is referred to as temura and is forbidden by the Torah (see 27:9-10). The Torah does not make clear, however, what level of sanctity the second animal will attain. Does it merely become the property of the Temple (kedushat bedek ha-bayit), or does it attain a level of inherent holiness (kedushat ha-guf)? And if it does attain inherent holiness, is it, too, destined for the altar as was the original animal?
The first Mishna places animals whose sanctity came by means of temura in the same category as offspring that were born of mothers that were destined for the altar, ruling that the offspring of a korban shelamim – a peace offering – as well as the temura of such a sacrifice, are in the same category as the original animal. Thus the second animal will be brought as a sacrifice, which includes semikha (the commandment that the individual who brings a sacrifice to the Temple must place his hands on the animal’s head, between its horns, leaning on the animal with all of his strength), wine libations, and the waving (giving to the priest) of the breast and thigh of the animal.
The Mishna applies this ruling to a korban shelamim, but it does not apply to all sacrifices. With regard to a korban ḥatat – a sin offering – for example, the law is that neither the offspring of a korban ḥatat nor the temura of a korban ḥatat can be brought on the altar and that the animal is left to die, since it cannot be used for any purpose – holy or mundane.