The Bible teaches us that the Holy Spirit is the Third Person of the Holy Trinity. Of course, the doctrine is not presented in the terms we have just used. However, the doctrine is certainly taught.
The Holy Spirit is called as the Spirit of God (Gen.1:1), the Spirit of Christ (Rom.8:9), and the Holy Spirit (Luke 24:49). He is also the Comforter, the Spirit of Truth (John 14:17), the Spirit of Glory (1Pet.4:14), the Spirit of Grace (Heb 10:29), the Spirit of Wisdom and Knowledge (Isa.11:2), and the Spirit of Life (Rom.8:2; Rev.11:11).
In Acts 5, lying against the Holy Spirit is pointed out as lying against God. Jesus declared the significance of the Person of the Holy Spirit in the words:
“Anyone who speaks a word against the Son of Man, it will be forgiven him; but whoever speaks against the Holy Spirit, it will not be forgiven him, either in this age or in the age to come.” (Matt.12:32).
This is so because the Holy Spirit is the Spirit of Grace and of Truth, the Lord who not only is the Prime Witness of Jesus Christ in this world (John 15:26), but also the one who convicts the world of sin, judgment, and righteousness (John 16:8).
He is the Holy Spirit of Promise who raised Jesus from the dead (Rom. 1:4; 8:11), is the guarantee of salvation sent by Christ to indwell those who receive Christ (Eph.1:14), and is the One who will also raise us from the dead in the Last Day at the appearance of Jesus Christ (Rom.8:11).
He is the testifier in our hearts that we are the children of God (Rom.8:16), He aids us in prayer and intercession (Rom.8:26), and empowers us with His might to be the witnesses of Christ in this world (Acts 1:8).
In his sermon, “Honey in the Mouth”, Spurgeon quotes Ralph Erskine saying this about the Holy Spirit:
“He speaks of grace as honey—honey for the cheering of the saints, for the sweetening of their mouths and hearts; but he says that in the Father “the honey is in the flower, which is at such a distance from us that we could never extract it.” In the Son “the honey is in the comb, prepared for us in our Immanuel, God-Man, Redeemer, the Word that was made flesh, saying, ‘All things that the Father hath are mine; and mine for your use and behoof’: it is in the comb. But then, next, we have honey in the mouth; the Spirit taking all things, and making application thereof, by showing them unto us, and making us to eat and drink with Christ, and share of these ‘all things’; yea, not only eat the honey, but the honeycomb with the honey; not only his benefits, but himself.” (“Honey in the Mouth”)