And the 132nd prohibition is that we are forbidden from eating pigul. Pigul is a sacrifice which becomes invalid because of an improper thought at the time of its slaughter or offering.1 As we explained and clarified in [the Commentary on the Mishneh] chapter 2 of Zevachim, this means that the one who performs the sacrifice had in mind that it will be eaten after the proper time or that the parts which need to be burned will be burned after the proper time.
The source of the prohibition of eating pigul is G‑d's statement,2 "Do not eat them, because they are holy," as we explained in the previous commandment.3 The punishment is derived from the verse4 in the Torah portion Tzav es Aharon regarding pigul, "If he eats from the offering on the third day, [the sacrifice] will not be accepted. It will be pigul and it will not be counted in his favor. Any person who eats it will bear his guilt."
The Oral Tradition explains that the verse refers to an offering which became invalid because of [improper] thought at the time of the offering, and this is what is called pigul; and that the phrase, "if he eats," refers only to one who had in mind that it will eaten on the third day. Our Sages say,5 "Pay attention and listen: this verse refers to one who thinks about his offering that it will be eaten on the third day." The offering becomes invalidated as a result of this thought, and one who eats from it after there was such a thought is punished by kares, as the verse says,6 "Any person who eats it will bear his guilt." [We know that this refers to kares] as it is written regarding nosar,7 "One who eats them8 shall bear his guilt [...This person shall be cut off (spiritually) from his people]." Our Sages say in tractate Kerisus9 "Don't treat a gezeira shava10 lightly, for pigul is one of the essential laws of Torah, and it is taught solely through a gezeira shava: comparing the word 'guilt' with the word 'guilt' used regarding nosar. Here it is written,11 'Any person who eats it will bear his guilt,' and there it is written,12 'One who eats them shall bear his guilt.' Just as there it refers to kares, so too here it refers to kares."
One who eats pigul accidentally must bring a sin offering.
The details of pigul and nosar have been explained in different places in Seder Kodshim.