Numbers 18:20

17 But no such payment may be made for the first birth of an ox or a sheep or a goat; these are holy: their blood is to be dropped on the altar, and their fat burned for an offering made by fire, a sweet smell to the Lord.

18 Their flesh is to be yours; like the breast of the wave offering and the right leg, it is to be yours.

19 All the lifted offerings of the holy things which the children of Israel give to the Lord, I have given to you and to your sons and to your daughters as a right for ever. This is an agreement made with salt before the Lord, to you and to your seed for ever.

20 And the Lord said to Aaron, You will have no heritage in their land, or any part among them; I am your part and your heritage among the children of Israel.

21 And to the children of Levi I have given as their heritage all the tenths offered in Israel, as payment for the work they do, the work of the Tent of meeting.

22 In future the children of Israel are not to come near the Tent of meeting, so that death may not come to them because of sin.

23 But the Levites are to do the work of the Tent of meeting, and be responsible for errors in connection with it: this is a law for ever through all your generations; and among the children of Israel they will have no heritage.