Numbers 18:26; Numbers 18:28

26 “Give these instructions to the Levites: When you receive from the people of Israel the tithes I have assigned as your allotment, give a tenth of the tithes you receive—a tithe of the tithe—to the LORD as a sacred offering.

28 You must present one-tenth of the tithe received from the Israelites as a sacred offering to the LORD . This is the LORD ’s sacred portion, and you must present it to Aaron the priest.