Numbers 18:20-23

20Then the Lord said to Aaron, ‘You priests and your descendants will have no land, like the other tribes do. You will not share in the things that they receive. I myself am the gift that you receive.

21The Israelites give to me one tenth of everything that they receive. I will give it to the Levites because they serve me in the Tent of Meeting.

22The other Israelites must not come near the Tent of Meeting again. If they do come near it, they will be guilty and then they will die.

23Only the Levites must do the work in the Tent of Meeting. And if they do anything wrong there, they will be guilty. That will be a rule for you and for all your descendants. The Levites will not receive any land like the other Israelites do.