Albert Barnes Commentary Exodus 12:10

"And ye shall let nothing of it remain until the morning; but that which remaineth of it until the morning ye shall burn with fire." — Exodus 12:10 (ASV)

This was afterwards a general law of sacrifices, at once preventing all possibility of profanity and of superstitious abuse. The injunction is on both accounts justly applied by our Church to the Eucharist.

Burn with fire – Not being consumed by man, it was thus offered, like other sacrifices (Exodus 12:8), to God.