Numbers 18:26-28

CLV(i) 26 As for the Levites, you shall speak and say to them:When you take from the sons of Israel the tithe which I give to you from them as your allotment, then you will raise up from it as a heave offering to Yahweh, a tenth of the tithe. 27 Your heave offering will be reckoned to you like the grain from the threshing site and like the fullness from the wine vat. 28 So shall you also raise up the heave offering of Yahweh from all your tithes which you take from the sons of Israel; and from it you will offer the heave offering of Yahweh to Aaron the priest.