Incidentally Hebrews is mainly about chastisement in context for believers. It was an exhortation to Jews who had been saved but then were tempted to return to an Old Testament worship system. It does not posit loss of salvation, anywhere. It is about microcosms, not about eternity.
Hebrews is a 4 course meal that describes the sin of man, the giving of the law to raise consciousness of sin, the inadequacy of the law and of animal sacrifices to cleanse our sin, the description of the priestly order of Aaron and the Levites compared and contrasted with the priestly order of Melchezidek of which Christ belonged, the description of Christ being that perfect final sacrifice, the judgement of those outside of Christ as being judged by the law signified by Mount Sinai as opposed to those who are in Christ Jesus (who are saved from the restrictions and condenmnation of the Law) (whose “final rest” is at Mount Zion),and the importance of staying in Grace.
The whole book describes the spiritual origin of our faith and what we have been saved and released from.