Numbers 18:21-29

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. 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. 29Out of all your gifts ye shall offer every heave-offering of Jehovah, of all the best thereof, even the hallowed part thereof out of it.