The Holy Spirit referred to as "God" - hence, part of the Triune Godhead

"There are occasions where Jesus speaks or prays to the Father,

making it clear there are two persons involved (Matthew 6:9).
In Acts 5:3-4 we find the Spirit specifically referred to as God: "Ananias, why has Satan filled your heart to lie to the Holy Spirit and to keep back for yourself part of the proceeds of the land? While it remained unsold, did it not remain your own? And after it was sold, was it not at your disposal? Why is it that you have contrived this deed in your heart? You have not lied to man but to God."
It is clear the Father is God (Deuteronomy 6:4), Jesus is God (John 1:1; Colossians 1:16), and the Spirit is God (Acts 5:3-4)."
CT