Numbers 18:21–26

²¹And unto the children of Levi, behold, I have given all the tithe in Israel for an inheritance, in return for their service which they serve, even the service of the tent of meeting. ²²And henceforth the children of Israel shall not come nigh the tent of meeting, lest they bear sin, and die. ²³But the Levites shall do the service of the tent of meeting, and they shall bear their iniquity: it shall be a statute for ever throughout your generations; and among the children of Israel they shall have no inheritance. 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.