Комментарий к Вайикра 7:18

אם האכל יאכל וגו' ‏ AND IF ANY [OF THE FLESH] SHOULD BE EATEN AT ALL [ON THE THIRD DAY) — Scripture is speaking of one who has the intention whilst slaughtering thė sacrifice to eat it (the flesh) on the third day. One might think that what the text really means is, that if one has eaten of it on the third day it becomes disqualified retrospectively (i. e., that it is regarded as having been invalid from the moment that it was offered)! Scripture, however, states, “As for him that offereth it, there shall be no מחשבה to him” implying that at the time when it is offered it can become disqualified, and that it cannot become disqualified on the third day (Sifra, Tzav, Section 8 1). And the following is its meaning (that of the text): At the time when it is offered, this shall not enter the mind of any priest performing a rite with it, to eat of it on the third day, and if he does harbour such a thought, it becomes פגול, an abominable thing,

ואם האכול יאכל, our sages ignored the plain meaning of this verse, interpreting it as referring to the owner planning to eat of the sacrificial meat on the third day [not provided for in the Torah. Ed.] or planning not to perform any of the 4 basic procedures during the time frame designated by the Torah. (Zevachim 29)

One who intends during the slaughtering. Meaning: If he had an invalid intention about it at the time the kohein sprinkles its blood, that is, to eat it on the third day, which is beyond its permitted time, then it is invalid. But after it was sacrificed, and all of its service was properly performed, no intention or action can invalidate it.