Numbers 18:21-28

21And, behold, I have given the children of Levi all the tenth in Israel for an inheritance, for their service which they serve, even the service of the tabernacle of the congregation. 22Neither must the children of Israel henceforth come nigh the tabernacle of the congregation, lest they bear sin, and die.1 23But the Levites shall do the service of the tabernacle of the congregation, and they shall bear their iniquity: it shall be a statute for ever throughout your generations, that among the children of Israel they have no inheritance. 24But the tithes of the children of Israel, which they offer as an heave offering unto Yhwh, I have given to the Levites to inherit: therefore I have said unto them, Among the children of Israel they shall have no inheritance.

25And Yhwh spake unto Moses, saying, 26Thus speak unto the Levites, and say unto them, When ye take of the children of Israel the tithes which I have given you from them for your inheritance, then ye shall offer up an heave offering of it for Yhwh, even a tenth part of the tithe. 27And this your heave offering shall be reckoned unto you, as though it were the grain of the threshingfloor, and as the fulness of the winepress. 28Thus ye also shall offer an heave offering unto Yhwh of all your tithes, which ye receive of the children of Israel; and ye shall give thereof Yhwh's heave offering to Aaron the priest.