Leviticus 10:10-12

10that ye may put difference between the holy and the unholy, and between unclean and clean,

11and that ye may teach the children of Israel all the statutes which Jehovah hath spoken to them by the hand of Moses.

12And Moses spoke to Aaron, and to Eleazar and to Ithamar, his sons that were left, Take the oblation that is left of Jehovah's offerings by fire, and eat it with unleavened bread beside the altar; for it is most holy.