Chapter Two, Mishnah 4. The Mishnah before us comes to expand upon what was stated in the last line of the previous Mishnah: a thought of 'beyond its time' - where the one offering intends to offer the korban or eat from it at a time that is not valid - incurs kares for eating the korban, provided that "sheyakriv hamatir kemitzvaso" - he offers the permitting agent according to its mitzvah, meaning that all the rest of the service was done properly, and the only invalidation is the thought of beyond its time. Therefore, the Mishnah elaborates with examples illustrating exactly when this condition is fulfilled, and when it is not.
What is the "matir":
The blood is called the 'matir', because the sacrificial parts may not be burned on the Altar and the meat may not be eaten until after the blood has been offered. The blood is therefore a necessary preliminary step, which permits the rest of the korban to be consumed - whether by the Altar, by the kohanim, or by the owners. For this reason, the blood must be offered first, and the blood service must be done entirely 'according to its mitzvah', properly and in the correct manner, besides the thought of 'beyond its time' that was introduced into it.
The Mishnah asks: "Keitzad karev hamatir kemitzvaso" - how is the permitting agent offered according to its mitzvah? In which cases is the korban processed in a way that the matir, the blood, was offered according to its mitzvah, and therefore the meat is piggul and one who eats it is liable to kares:
"Shachat bishtikah, kibel vehilech vezarak chutz lizmano" - if he slaughtered in silence, and received, carried, and sprinkled beyond its time. The slaughtering was done routinely, without any invalidating factor; whereas during the receiving of the blood, carrying it, and sprinkling it, he intended to eat or burn the relevant part on the Altar at an invalid time. This is a pure invalidation of 'beyond its time', and therefore the korban is piggul.
"O sheshachat chutz lizmano, kibel vehilech vezarak bishtikah" - or if he slaughtered beyond its time, and received, carried, and sprinkled in silence. The slaughtering was done with a thought of beyond its time, whereas the receiving, carrying, and sprinkling were done without any additional issue.
"O sheshachat vekibel vehilech vezarak chutz lizmano" - or if he slaughtered, received, carried, and sprinkled beyond its time. He performed one of these services, or all of them, with a thought of beyond its time, and without any other invalidating factor.
In all of these, "zehu shekarev hamatir kemitzvaso" - this is when the permitting agent is offered according to its mitzvah. The blood was offered as it should have been done, besides the thought of beyond its time, and therefore the korban is piggul and one who eats from it is liable to kares.
It is appropriate to note the Mishnah's phrasing of "bishtikah" - in silence. The simple understanding is that the slaughtering was done without an invalidating thought - not for another purpose, not beyond its place, and so forth. However, some derive from here: if the intention is that there was nothing invalid in it, it should have said "he slaughtered ordinarily" (stam); so why did the Mishnah state "bishtikah", which literally means quietly? From here, some commentators learned that for the invalidating thought to invalidate, it is not enough for him to think it in his heart; rather, he must express it with his mouth, and if he did not express it verbally, it is irrelevant. However, this is not the opinion of the Bartenura, nor the opinion of the Rema.
The permitting agent was not offered according to its mitzvah:
What are the cases where the blood was not offered according to its mitzvah? This means that even though the person had thoughts of beyond its time in one of the four blood services, other invalidating thoughts were combined with them, and because of this the korban is not piggul and there is no liability of kares for eating it, since it is not a pure invalidation of 'beyond its time':
"Shachat chutz limkomo, kibel vehilech vezarak chutz lizmano" - if he slaughtered beyond its place, and received, carried, and sprinkled beyond its time. The slaughtering was done with a thought of beyond its place, which is not a thought of beyond its time, whereas the receiving, carrying, or sprinkling were done with a thought of beyond its time.
"O sheshachat chutz lizmano, kibel vehilech vezarak chutz limkomo" - or if he slaughtered beyond its time, and received, carried, and sprinkled beyond its place. The piggul thought of beyond its time came first during the slaughtering, but during the receiving, carrying, or sprinkling, a thought of beyond its place was combined with it.
"O sheshachat kibel vehilech vezarak chutz limkomo" - or if he slaughtered, received, carried, and sprinkled beyond its place. In addition to the thought of beyond its time that he had, he performed one of the services, or all of them, with a thought of beyond its place.
In all of these, the invalidation is not beyond its time alone, and therefore there is no liability of kares for eating the meat.
The pesach and the chatas:
As we recall from the first chapter, these two offerings become invalid through a thought of 'not for their sake' - when the person has in mind a different type of offering. This unique rule applies only to the Pesach and chatas:
"Hapesach vehachatas sheshachtan shelo lishman, kibel vehilech vezarak chutz lizmano" - For example, he took a chatas and slaughtered it with the thought that he is slaughtering an asham, thereby invalidating the offering; and afterward he received the blood, carried it, or sprinkled it with the intention to burn it on the altar or eat it at an invalid time. This is not solely an issue of outside its time, because the thought of not for their sake was combined here, which invalidates a chatas and a Pesach, and therefore there is no liability for kares.
"O sheshachat chutz lizmano, kibel vehilech vezarak shelo lishman" - The slaughter was done with a thought of outside its time, and seemingly the offering was destined to become pigul, except that during the receiving, carrying, or sprinkling, a thought of not for their sake was combined, as he had the wrong offering in mind. This is referring to a chatas, or a Pesach at its proper time.
"O sheshachat kibel vehilech vezarak shelo lishman" - In addition to the thoughts of outside its time that he had, he performed the slaughter, receiving, carrying, or sprinkling with a thought about another offering, which is not a chatas or Pesach, depending on the case.
In summary: We have learned both sides of the rule. "Karev hamatir kemitzvaso" - the blood was offered properly, and the only invalidation is a thought of outside its time, and therefore the offering is pigul and one who eats a kezayis of its meat is liable for kares. However, when the permitting factor was not offered in accordance with its mitzvah, meaning that during the application of the blood, other invalidations were combined besides outside its time - outside its place, or not for their sake in the case of a Pesach or chatas - then even though the offering is absolutely invalid, it does not carry the kares penalty of a pigul offering.