Numbers 18:26-28

18:26 “You are to speak to the Levites, and you must tell them, ‘When you receive from the Israelites the tithe that I have given you from them as your inheritance, then you are to offer up from it as a raised offering to the Lord a tenth of the tithe. 18:27 And your raised offering will be credited to you as though it were grain from the threshing floor or as new wine from the winepress. 18:28 Thus you are to offer up a raised offering to the Lord of all your tithes which you receive from the Israelites; and you must give the Lord’s raised offering from it to Aaron the priest.