Leviticus 6:19

All the males among the children of Aaron shall eat of it. It shall be a statute for ever in your generations concerning the offerings of the LORD made by fire: every one that toucheth them shall be holy.

This is the offering of Aaron and of his sons, which they shall offer unto the LORD in the day when he is anointed; the tenth part of an ephah of fine flour for a meat offering perpetual, half of it in the morning, and half thereof at night.