Numbers 18:25-28
Instructions for the Levites
18:25 The Lord spoke to Moses:
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.