Charles Ellicott Commentary Leviticus 7:18

"And if any of the flesh of the sacrifice of his peace-offerings be eaten on the third day, it shall not be accepted, neither shall it be imputed unto him that offereth it: it shall be an abomination, and the soul that eateth of it shall bear his iniquity." — Leviticus 7:18 (ASV)

And if any of the flesh ... be eaten. — The owner of the sacrifice was responsible for the proper observance of this instruction. If, through his neglect, anyone ate from the sacrifice after the limited time specified here, the effectiveness of the sacrifice was annulled, and the offerer had to bring another votive offering.

It shall be an abomination. — This means that the flesh, when left for so long in the Eastern climate, begins to putrefy and becomes loathsome and offensive by the third day; thus, what is holy becomes desecrated.

And the soul that eateth of it. — Therefore, whoever ate it after the prescribed time was regarded as eating carrion and bore his guilt; that is, he incurred the penalty of excision.