Who is the Holy Spirit?
He is not an impersonal force. He is not just another word for God's "power" at work.
The Holy Spirit is the third Person of the Trinity.
What's the Trinity? The Bible reveals that altough God is One, He exists in three distinct and equal Persons: Father, Son, and Spirit. All three possess 100% of the attributes of God. So it's not just three different names for God, nor that each is 1/3 of God. Each is fully God, but distinct.
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By "person" we don't mean a human being, but a being with their own intellect, emotion, and will. Just as God the Father and God the Son (Jesus!) have a distinct intellect, emotion, and will, so does God the Spirit.
The Spirit has intellect and will He uses to choose our spiritual gifts for ministry:
But one and the same Spirit works all these things, distributing to each one individually just as He wills (1 Corinthians 12:11)
The Holy Spirit has emotions:
Do not grieve the Holy Spirit of God, by whom you were sealed for the day of redemption (Ephesians 4:30).
And He is given equal standing to the Father and Son. We are told to baptize in the Spirit's name too:
Therefore go and make disciples of all nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit (Matthew 28:19).