Numbers 18:25-32

25Adonai spoke to Moses saying,

26“Speak now to the Levites and say to them: When you receive from Bnei-Yisrael the tithe which I have given to you as your inheritance, you are then to offer to Adonai a tithe of that tithe.

27Your offering will be reckoned as grain from the threshing floor or the fullness of the winepress.

28Thus you will also present an offering to Adonai from all your tithes that you receive from Bnei-Yisrael, and from that you are to give Adonai’s portion to Aaron the kohen.

29From all your gifts that you receive, you are to present the best and holiest from them as Adonai’s portion.

30“Say to them: When you present the best part, it will be reckoned to the Levites as the produce of the threshing floor and of the winepress.

31You and your household may eat it in any place. It is your wage for your service in the Tent of Meeting.

32“In presenting the best part in this manner, you will bear no guilt in these matters. You will not defile the holy things of Bnei-Yisrael, so you will not die.”