Numbers 18:24-28

24For the tithe of the children of Israel, which they offer as a heave-offering unto Jehovah, I have given to the Levites for an inheritance: therefore I have said unto them, Among the children of Israel they shall have no inheritance.

25And Jehovah spake unto Moses, saying, 26Moreover thou shalt speak unto the Levites, and say unto them, When ye take of the children of Israel the tithe which I have given you from them for your inheritance, then ye shall offer up a heave-offering of it for Jehovah, a tithe of the tithe. 27And your heave-offering shall be reckoned unto you, as though it were the grain of the threshing-floor, and as the fulness of the winepress. 28Thus ye also shall offer a heave-offering unto Jehovah of all your tithes, which ye receive of the children of Israel; and thereof ye shall give Jehovah’s heave-offering to Aaron the priest.