15-17. the flesh of the sacrifice of his peace offerings . . . shall be eaten the same day that it is offered—The flesh of the sacrifices was eaten on the day of the offering or on the day following. But if any part of it remained till the third day, it was, instead of being made use of, to be burned with fire. In the East, butcher-meat is generally eaten the day it is killed, and it is rarely kept a second day, so that as a prohibition was issued against any of the flesh in the peace offerings being used on the third day, it has been thought, not without reason, that this injunction must have been given to prevent a superstitious notion arising that there was some virtue or holiness belonging to it.

     18. if any of the flesh of the sacrifice . . . be eaten at all on the third day, it shall not be accepted, neither . . . imputed—The sacrifice will not be acceptable to God nor profitable to him that offers it.

     5-8. if ye offer a sacrifice of peace offerings unto the Lord, ye shall offer it at your own will—Those which included thank offerings, or offerings made for vows, were always freewill offerings. Except the portions which, being waved and heaved, became the property of the priests (see Le 3:1-17), the rest of the victim was eaten by the offerer and his friend, under the following regulations, however, that, if thank offerings, they were to be eaten on the day of their presentation; and if a freewill offering, although it might be eaten on the second day, yet if any remained of it till the third day, it was to be burnt, or deep criminality was incurred by the person who then ventured to partake of it. The reason of this strict prohibition seems to have been to prevent any mysterious virtue being superstitiously attached to meat offered on the altar.