Numbers 18:25

22 Neither must the children of Israel henceforth come nigh the tabernacle of the congregation, lest they bear sin, and die.

23 But 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.

24 But the tithes of the children of Israel, which they offer [as] a heave-offering to the LORD, I have given to the Levites to inherit: therefore I have said to them, Among the children of Israel they shall have no inheritance.

25 And the LORD spoke to Moses, saying,

26 Thus speak to the Levites, and say to 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 a heave-offering of it for the LORD, [even] a tenth [part] of the tithe.

27 And [this] your heave-offering shall be reckoned to you, as though [it were] the corn of the threshing-floor, and as the fullness of the wine-press.

28 Thus ye also shall offer a heave-offering to the LORD of all your tithes which ye receive of the children of Israel; and ye shall give of them the LORD'S heave-offering to Aaron the priest.