Leviticus 7 · a question people ask
Why was eating it on the third day so serious?
Verse 18 says what happens, not why: the sacrifice "will not be accepted, and it shall not be credited to him who offers it. It will be an abomination, and the soul who eats any of it will bear his iniquity" (7:18). Whatever was left by then "shall be burned with fire" (7:17). Leviticus 19 repeats the rule and gives a reason: "because he has profaned the holy thing of the LORD" (19:8). The thanksgiving had a shorter limit still: "He shall not leave any of it until the morning" (7:15; also 22:30). Leviticus doesn't say why the limit falls on the third day.
The verses
““‘When you offer a sacrifice of peace offerings to the LORD, you shall offer it so that you may be accepted. It shall be eaten the same day you offer it, and on the next day. If anything remains until the third day, it shall be burned with fire. If it is eaten at all on the third day, it is an abomination. It will not be accepted; but everyone who eats it shall bear his iniquity, because he has profaned the holy thing of the LORD, and that soul shall be cut off from his people.”
““When you sacrifice a sacrifice of thanksgiving to the LORD, you shall sacrifice it so that you may be accepted. It shall be eaten on the same day; you shall leave none of it until the morning. I am the LORD.”