Numbers 18:25-32 - Instructions For The Levites
25 And the LORD spake unto Moses, saying, 26 "Speak unto the Levites and say unto them, 'When ye take of the children of Israel the tithes which I have given you of them to your inheritance, ye shall take a heave offering of that same for the LORD: even the tenth of that tithe. 27 And it shall be reckoned unto you for your heave offering, even as though ye gave corn out of the barn or a full offering from the wine press. 28 And of this manner ye shall heave a heave offering unto the LORD, of all your tithes which ye receive of the children of Israel, and ye shall give thereof the LORD's heave offering unto Aaron the priest. 29 Of all your gifts, ye shall take out the LORD's heave offering: even the fat of all their hallowed things.'
30 "And thou shalt say unto them, 'When ye have taken away the fat of it from it, it shall be counted unto the Levites, as the increase of corn and wine. 31 And ye shall eat it in all places, both ye and your households, for it is your rewards for your service in the tabernacle of witness. 32 And ye shall bear no sin by the reason of it, when ye have taken from it the fat of it: neither shall ye unhallow the hallowed things of the children of Israel, and so shall ye not die.'"