Numbers 18:24-28

24But the tithes of the children of Israel, which they offer as an 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. 25And the LORD spoke to Moses, saying, 26Thus 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 an heave offering of it for the LORD, even a tenth part of the tithe. 27And this your heave offering shall be reckoned to 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 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.