After setting aside the heave-offering for the priests one sets aside a tenth of the remainder for the Levites; this is called the first tithe. Anyone can eat it, even an Israelite who is impure, once the tithe of the tithe has been set aside from it. Ezra ordained that the tithe should be given to the priests rather than the Levites.^a

Sources:
	a. 1:1-2,4