Especially Hebrews 9:14 establishes the Spirit’s essence from all eternity past and unto all eternity future. As the Westminster Confession of Faith observes:8 "The Lord Jesus, by His perfect obedience and sacrifice of Himself, which He through the eternal Spirit once [and for all] offered up unto God — hath fully satisfied the justice of His Father. Hebrews 9:14."
2. The Holy Spirit’s Personality
Being God Himself, the Holy Ghost is not just a thing or an influence or a power. To the contrary, He is a living Person. Consequently, the Bible often uses personal pronouns and possessive adjectives (like "He" and "His") to refers to the Spirit.