As a Member of the Godhead, the Holy Spirit was present before time, and will remain after “time shall be no more.”
The writer of the book of Hebrews recognized His eternal nature when he wrote that if the blood of bulls and goats was once used as a sacrifice, “how much more shall the blood of Christ, who through the eternal Spirit offered Himself without spot to God, purge your conscience from dead works to serve the living God?” (Heb. 9:14 Kjv, emphasis added).
Just as the Melchizedekian priesthood of Christ is superior to the priesthood of the Old Testament law, so the redemption effected through the eternal Spirit is superior to the temporary remedies of the law—remedies designed not so much to redeem man as to point out man’s need for redemption through faith in Christ.
That He is an “eternal Spirit” is as much as saying He is a “divine Spirit.” “The term eternal, which with all propriety can also be assigned to God the Father or God the Son, is here assigned to the Holy Spirit. Since of God alone this attribute may be predicated, the Spirit is understood as God.” 11