Numbers 18:24-28

24Instead, I will give the Levites what the Israelites contribute to the Lord—one-tenth of the Israelites’ income. This is why I said about them, ‘They will own no property as the other Israelites do.’ ”

25The Lord said to Moses,

26“Speak to the Levites and say to them: You will take one-tenth of the Israelites’ income which I’m giving you as your property. When you do, you must contribute one-tenth of that income as your contribution to the Lord.

27Your contribution will be considered to be grain from the threshing floor  or juice from the winepress.

28So you, too, will contribute one-tenth of your income to the Lord out of all that you receive from the Israelites’ income. You will give the Lord’s contribution to the priest Aaron.