Numbers 18:24-27

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

²⁵And the Lord spoke unto Moses, saying,

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

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