Our Gospel gives us one of the Bible’s most powerful readings, and the first reading from Leviticus bears some relationship to it. In the Gospel Jesus lays out the manner of life we must live if we want to be in a relationship with him. (We too must feed, clothe, visit the needy.) In the passage from Leviticus God laid out the manner of life the Israelites had to live if they wanted a real relationship with him.
Another way of saying that is that the Gospel laid out the terms for the New Covenant, while the first reading laid out the terms for the Old Covenant. People who pay any attention to me grow tired of my bringing up the subjects of covenants, but I can’t avoid it.
Marriage is our most common covenant. But, in all covenants two parties become one by giving themselves to each other. In marriage the parties can only achieve oneness by sacrifices on both sides, where each party changes his and her ways, doing away with traits that keep them apart.
A covenant with God can’t work that way. All his ways are perfect. Oneness with God can only be achieved by the human giving up his or her sinful ways.
It was somewhat the same with commoners entering into a covenant with their feudal lord. Oneness could only be achieved by their wearing his livery. That’s why God in Leviticus said, “Be holy, for I, the Lord, am holy”