Numbers 18:25-28

25And Jehovah spoke to Moses, saying,

26And to the Levites shalt thou speak, and say unto them, When ye take of the children of Israel the tithes which I have given you from them for your inheritance, then ye shall offer a heave-offering from it for Jehovah, the tenth of the tithe.

27And your heave-offering shall be reckoned unto you, as the corn from the threshing-floor, and as the fulness of the winepress.

28Thus ye also shall offer Jehovah's heave-offering of all your tithes, which ye take of the children of Israel; and ye shall give thereof Jehovah's heave-offering to Aaron the priest.