Numbers 18:26-28

“Speak to the Levites and tell them: ‘You will receive a tenth of everything the Israelites make, which I will give to you. But you must give a tenth of that back to the LORD. I will accept your offering just as much as I accept the offerings from others, who give new grain or new wine. In this way you will present an offering to the LORD as the other Israelites do. When you receive a tenth from the Israelites, you will give a tenth of that to Aaron, the priest, as the LORD’s share.