Numbers 18:21-18:32

And to the Levites I hereby give all the tithes in Israel as their share in return for the services that they perform, the services of the Tent of Meeting. Henceforth, Israelites shall not trespass on the Tent of Meeting, and thus incur guilt and die: only Levites shall perform the services of the Tent of Meeting; others would incur guilt. It is the law for all time throughout the ages. But they shall have no territorial share among the Israelites; for it is the tithes set aside by the Israelites as a gift to the Lord that I give to the Levites as their share. Therefore I have said concerning them: They shall have no territorial share among the Israelites. The Lord spoke to Moses, saying: Speak to the Levites and say to them: When you receive from the Israelites their tithes, which I have assigned to you as your share, you shall set aside from them one-tenth of the tithe as a gift to the Lord. This shall be accounted to you as your gift. As with the new grain from the threshing floor or the flow from the vat, so shall you on your part set aside a gift for the Lord from all the tithes that you receive from the Israelites; and from them you shall bring the gift for the Lord to Aaron the priest. You shall set aside all gifts due to the Lord from everything that is donated to you, from each thing its best portion, the part thereof that is to be consecrated. Say to them further: When you have removed the best part from it, you Levites may consider it the same as the yield of threshing floor or vat. You and your households may eat it anywhere, for it is your recompense for your services in the Tent of Meeting. You will incur no guilt through it, once you have removed the best part from it; but you must not profane the sacred donations of the Israelites, lest you die.