Numbers 18:26-32

26“Speak to the Levites and tell them: ‘When you receive from the Israelites the tithe that I have given you as your inheritance, you must present part of it as an offering to the LORD—a tithe of the tithe. 27Your offering will be reckoned to you as grain from the threshing floor or juice from the winepress. 28So you are to present an offering to the LORD from all the tithes you receive from the Israelites, and from these you are to give the LORD’s offering to Aaron the priest. 29You must present the offering due the LORD from all the best of every gift, the holiest part of it.’

30Therefore say to the Levites, ‘When you have presented the best part, it will be reckoned to you as the produce of the threshing floor or winepress. 31And you and your households may eat the rest of it anywhere; it is the compensation for your work at the Tent of Meeting. 32Once you have presented the best part of it, you will not incur guilt because of it. But you must not defile the sacred offerings of the Israelites, or else you will die.’”