Traditional churches teach that God is a trinity and that the Holy Spirit is a person. But if this was the teaching of the first century Church, why do we not read of controversy with the Jews about the nature of the Holy Spirit in the New Testament books of Acts and the epistles?
The Jews knew the Holy Spirit, also called the Spirit of God, exists. There are references to the Spirit of God in the Old Testament. Here are some examples.
"The earth was without form, and void; and darkness was on the face of the deep. And the Spirit of God was hovering over the face of the waters" (Genesis 1:2).
"And Pharaoh said to his servants, 'Can we find such a one as this, a man in whom is the Spirit of God?' Then Pharaoh said to Joseph, 'Inasmuch as God has shown you all this, there is no one as discerning and wise as you' " (Genesis 41:38-39).
"Then the Lord spoke to Moses, saying: 'See, I have called by name Bezalel the son of Uri, the son of Hur, of the tribe of Judah. And I have filled him with the Spirit of God, in wisdom, in understanding, in knowledge, and in all manner of workmanship, to design artistic works, to work in gold, in silver, in bronze, in cutting jewels for setting, in carving wood, and to work in all manner of workmanship" (Exodus 31:1-5).
"As they were going down to the outskirts of the city, Samuel said to Saul, 'Tell the servant to go on ahead of us.' And he went on. 'But you stand here awhile, that I may announce to you the word of God' " (1 Samuel 9:27). "Then the Spirit of the Lord will come upon you, and you will prophesy with them and be turned into another man" (1 Samuel 10:6). "So it was, when he had turned his back to go from Samuel, that God gave him another heart; and all those signs came to pass that day. When they came there to the hill, there was a group of prophets to meet him; then the Spirit of God came upon him, and he prophesied among them" (1 Samuel 10:9-10).
"Now the Spirit of God came upon Azariah the son of Oded. And he went out to meet Asa, and said to him: 'Hear me, Asa, and all Judah and Benjamin. The Lord is with you while you are with Him. If you seek Him, He will be found by you; but if you forsake Him, He will forsake you' " (2 Chronicles 15:1-3).
"The Spirit of God has made me, and the breath of the Almighty gives me life" (Job 33:4).
"Then Samuel took the horn of oil and anointed him in the midst of his brothers; and the Spirit of the Lord came upon David from that day forward. So Samuel arose and went to Ramah" (1 Samuel 16:13).
"Do not cast me away from Your presence, and do not take Your Holy Spirit from me" (Psalm 51:11).
The Jews understood that the Spirit of God was God's mind and power in action, just as we understand it today in the Church of God, but not a person, like a third person of a trinity, as traditional, mainstream churches believe today.
The early Church must have understood the truth about the nature of God and whether the Spirit of God is a person distinct from God the Father and Jesus Christ, as today's mainstream churches teach, or the power of God that comes from God, as the Jews believed. And if the first century Church taught that the Holy Spirit is a person, that would have created as great a controversy with the Jews as the teaching that Jesus Christ is God. Yet we see no evidence in New Testament writings that there was any controversy between the Church and the Jews about the Holy Spirit.
But there was plenty of controversy about Jesus Christ.
The Jews thought of God as one person. Any teaching that Jesus Christ, a person distinct from God the Father, was also God, came across to the Jews as teaching that there is more than one God, which would have been idolatry. We understand that the Father and Christ are two persons but one God, that is, one God family. But the Jews would never accept the concept of one God but more than one person who is God.
That same difficulty for the Jews would appear if the early Church taught that the Holy Spirit was a person, distinct from God the Father, yet also God. That would have seemed to the Jews to be just as much a teaching of multiple gods as teaching that Jesus is God, and they would have labeled it idolatry and heresy.
Why do we read of no controversy about the Holy Spirit in the book of Acts or the epistles? There was no controversy because the original, first century Church did not change the doctrine of the Jews that the Spirit of God is the power of God by which He acts in His creation, an understanding they got from the Old Testament.
The lack of controversy between the Jews and the first century Church about the nature of the Holy Spirit is one more point of evidence that the early Church did NOT teach that the Holy Spirit is a person, and therefore did not teach that God is a trinity.
Here are links to related chapters or sections in Preaching the Gospel:
God's Purpose for Mankind, Chapter 2
The Holy Spirit, Chapter 2