Numbers — Chapter 18

Aaron and his sons bear the iniquity of the sanctuary; if any layman comes too near and dies, the priests are held responsible — they stand between God's holiness and the people's weakness.

God grants to Aaron the custody of the firstfruits and holy offerings; all that is sanctified belongs to the priests as their perpetual due — God Himself is their inheritance, not any earthly portion.

God assigns tithes to the Levites as their inheritance in return for their service; from these tithes the Levites in turn give a tithe to the priests — the layered system of sacred support for those who serve the altar.