Albert Barnes Commentary Leviticus 7:18-19

"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. And the flesh that toucheth any unclean thing shall not be eaten; it shall be burnt with fire. And as for the flesh, every one that is clean shall eat thereof:" — Leviticus 7:18-19 (ASV)

It was proper that the sacrificial meat should not be polluted by any sign of decay. But the exclusion of a spirit of stinginess may also have provided the basis for the distinction between the thank-offerings and the others. The most generous distribution of the meat from the offering, particularly among the poor who were invited to partake, would clearly be appropriate when the sacrifice was intended especially to express gratitude for mercies received.