Hebrews 8 talks about the establishment of the new covenant, and this is not a brand new covenant. This covenant was promised in the Old Testament. In fact, he quotes from Jeremiah 31, the promise of a new covenant. God made a covenant with Israel at Mount Sinai, but he promises that one day — Israel had broken that covenant — and one day God would reestablish a new covenant, and that new covenant wouldn't have the law written on tablets of stone. It would have the law written on our hearts. It would not provide just temporal temporary forgiveness of sins, it would provide eternal forgiveness of sins. You wouldn't need a mediator to go through the priest. You would know God. All God's people would know God through the Messiah, through Jesus Christ. So, the promise of the new covenant in Jeremiah 31 has come to fulfillment, and that's what the author is arguing. And with that promise of fulfillment, God's salvation is now not just for Israel, but is going forth to all nations everywhere. So, all along, the author says, this is what God had intended, this the fulfillment of the promises. He tells the audience, "Don't go back. Don't go back to your old way. Don't go back to the shadow. Don't go back to the promise, because the fulfillment has arrived. We are under the new covenant, not the old Mosaic covenant."