Numbers 18:24-27

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.