In speaking of a new covenant, he makes the first one obsolete. And what is becoming obsolete and growing old is ready to vanish away.
13. In that he saith, A new, etc. From the fact of one covenant being established, he infers the subversion of the other; and by calling it the old covenant, he assumes that it was to be abrogated; for what is old tends to a decay.
In this part of the chapter, the apostle illustrates and confirms the superior excellency of the priesthood of Christ above that of Aaron, from the excellency of that covenant, or that dispensation of the covenant of grace, of which Christ was the Mediator (Heb 8:6): his ministry is more excellent, by how much he is the Mediator of a better covenant.
Commenting on Hebrews 8:6-13
In that he saith a new covenant,.... In the above prophecy, Heb 8:8 he hath made the first old; this naturally follows from hence; if the second is new, the first must be old; which is called so, not on account of its date and duration; for the covenant of grace itself is older than this mode of administration of it, and the manifestation of...