Numbers 18:24-27

²⁴For the tithe of the children of Israel, which they set apart as a gift unto the LORD, 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 the LORD spoke unto Moses, saying:

²⁶'Moreover 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 set apart of it a gift for the LORD, even a tithe of the tithe.

²⁷And the gift which ye set apart shall be reckoned unto you, as though it were the corn of the threshing-floor, and as the fulness of the wine-press.