Hebrews 12:26-28 is the fulfillment of Paul’s words in Galatians 4:30. The casting out of the bondwoman (Old Covenant) and her son (Old Covenant Israel) took place so that the New Covenant could be established, and her sons (true Israel) could received the inheritance of Abraham as the kingdom of God. (Mathew 25:34)
The Institute Of Fulfilled Eschatology