Numbers 18:26-28

New Revised Standard Version, Anglicised Catholic Edition

²⁶ You shall speak to the Levites, saying: When you receive from the Israelites the tithe that I have given you from them for your portion, you shall set apart an offering from it to the Lord, a tithe of the tithe. ²⁷ It shall be reckoned to you as your gift, the same as the grain of the threshing-floor and the fullness of the wine press. ²⁸ Thus you also shall set apart an offering to the Lord from all the tithes that you receive from the Israelites; and from them you shall give the Lord’s offering to the priest Aaron.