The author’s summary:
The above discussion has attempted to connect the warnings of Hebrews with the blessings and the curses associated with covenant faithfulness/unfaithfulness in the OT. Doing so leads us to conclude that these warning texts do indeed lend themselves to the possibility that an individual in covenant relationship with God can by deliberate unfaithfulness to the covenant be excluded from that relationship. The basis for this association arises from the author’s utilization of the old covenant expression “good word” (i.e. the promised blessing) and his categorizing the sin of apostasy as being beyond the remedy of atonement (i.e. the warned curse).