Conscience

If we try to summarise the whole of Hebrews in one sentence, we are very much helped by two markers which bookend the central section.
It turns out that our confidence that Jesus has washed us perfectly clean from sin is the central focus of the book.

Washed Clean, Forever, by a Single Offering — Heb 10:1-23 (pt.12)

Since we have authorization for free access to enter the sanctuary by the blood of Jesus, by the fresh and living way that he opened up for us, through the curtain—that is through his flesh,
let us draw near with a sincere heart in the assurance that faith brings,
because we have had our hearts sprinkled clean from a burdened conscience and our bodies washed in pure water.
And let us hold unwaveringly to the hope that we confess, for the one who made the promise is trustworthy.