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.

JFB.