When I Googled the subject "Trinity" it said that it was Tertullian who in the third century AD began to advocate that the Holy Spirit is a person.
I don't believe in the Trinity, the concept that there are THREE Persons in the Israelite Godhead.
I only believe that there are TWO Persons in the Israelite Godhead.
There is God the Father of the Old Testament and there is God the Son.
As for God the Father:
Deuteronomy 6:4
Hear, O Israel: The LORD our God is one LORD.
(The above word "LORD" is the word "Yehova" in Hebrew)
And this God Jehova has a Son:
Psalm 2:12
Kiss the Son, lest he be angry, and you perish from the way, when his wrath is kindled but a little.
Galatians 4:4
But when the fulness of the time was come, God sent forth his Son, made of a woman.
But the most important Biblical evidence that there are only TWO Persons in the Israelite Godhead is found in the letters of Paul.
At the beginning of ALL Paul's letters, Paul ONLY BRINGS GREETINGS to the Church from GOD THE FATHER and from the LORD JESUS CHRIST ... and then, Paul... STOPS! Let's look at those verses:
Romans 1:7
To all that be in Rome, beloved of God, called to be saints: Grace to you and peace from God our Father, and the Lord Jesus Christ.
1 Corinthians 1:3
Grace be to you, and peace, from God our Father, and from the Lord Jesus Christ.
2 Corinthians 1:2
Grace be to you and peace from God our Father, and from the Lord Jesus Christ.
Galatians 1:3
Grace be to you and peace from God the Father, and from our Lord Jesus Christ.
Ephesians 1:2
Grace be to you, and peace, from God our Father, and from the Lord Jesus Christ.
Philippians 1:2
Grace be to you, and peace, from God our Father, and from the Lord Jesus Christ.
Colossians 1:2
To the saints and faithful brethren in Christ who are at Colosse: Grace be to you, and peace, from God our Father and the Lord Jesus Christ.
1 Thessalonians 1:1
Paul and Silvanus and Timotheus, to the church of the Thessalonians which is in God the Father and in the Lord Jesus Christ: Grace be to you, and peace, from God our Father, and the Lord Jesus Christ.
2 Thessalonians 1:2
Grace to you, and peace, from God our Father and the Lord Jesus Christ.
1 Timothy 1:2
To Timothy, my own son in the faith: Grace, mercy, and peace, from God our Father and Jesus Christ our Lord.
2 Timothy 1:2
To Timothy, my dearly beloved son: Grace, mercy, and peace, from God the Father and Christ Jesus our Lord.
Titus 1:4
To Titus, my own son after the common faith: Grace, mercy, and peace, from God the Father and the Lord Jesus Christ our Saviour.
Philemon 1:3
Grace to you, and peace, from God our Father and the Lord Jesus Christ.
NOW, if Paul had considered the Holy Spirit to be a Person, would not Paul also have sent greetings from the Holy Spirit to the Church?
Indeed, the Bible says instead that the Spirit is the Spirit of God and the Spirit of Jesus Christ:
1 Corinthians 3:16
Don't you know that you are the temple of God, and that the Spirit of God dwells in you?
Galatians 4:6
And because you are sons, God has sent forth the Spirit of his Son into your hearts, crying, Abba, Father.
So clearly the Spirit is something that belongs to God the father and that belongs to God the Son.
Again, if anyone in the New Testament would have known whether the Holy Spirit was a person like God the Father and like God the Son ... Paul would have certainly known it and Paul would also have sent greetings from the Holy Spirit and the reason Paul NEVER did is because Paul knew that the Holy Spirit was not a person.
There are only TWO Persons in the Israelite Godhead, God the Father and God the Son Jesus Christ.
It was Tertullian who in the third century AD floated the idea that the Holy Spirit was a person and the modern church has adopted it Hook, Line & Sinker.