Pesachim 96A

מהו? מדאישתרי טומאת בשר ⁠— אישתרי נמי טומאת אימורין, או דילמא: מאי דאישתרי ⁠— אישתרי, מאי דלא אישתרי ⁠— לא אישתרי.

what is the halakha? Are they liable for eating sacrificial meat while they were ritually impure? Do we say that since ritual impurity of the meat that is eaten was permitted, ritual impurity of the sacrificial portions offered on the altar was also permitted; or perhaps we say that what was permitted was permitted, and what was not permitted was not permitted?

אמר רבא: מכדי טומאת אימורין מהיכא איתרבי ⁠— מטומאת בשר, דכתיב: ״אשר לה׳״, לרבות את האימורין.

Rava said: After all, from where was the halakha pertaining to eating the sacrificial portions in a state of ritual impurity included? It is derived from the halakha with regard to eating the meat in a state of ritual impurity, as it is written: “But the soul that eats of the flesh of the sacrifice of peace-offerings that pertain to YHWH, having his ritual impurity upon him, that soul should be cut off from his people” (Leviticus 7:20); the apparently superfluous phrase “that pertain to YHWH” is there to include the sacrificial portions and establish that one is liable to receive karet for eating these portions in a state of ritual impurity.

כל היכא דאיתיה לטומאת בשר, איתיה לטומאת אימורין. כל היכא דליתיה לטומאת בשר, ליתיה לטומאת אימורין.

Since this is the source, there is a limitation to the halakha pertaining to sacrificial portions: Anywhere that there is liability for eating the meat in a state of ritual impurity, there is liability for eating the sacrificial portions in a state of ritual impurity; conversely, anywhere that there is no liability for eating the meat in a state of ritual impurity, such as in the case of a Paschal lamb offered in a state of ritual impurity, there is no liability for eating the sacrificial portions in a state of ritual impurity.