There is one God, who eternally exists as three Persons: Father, Son, and Holy Spirit, the same in essence, distinct in Person. Scripture does not give this as a philosophy; it shows it in the life of God revealed in Christ and in the work of salvation.
Not a summary of these passages: the passages themselves. Read them, then come back to the study below.
The study
What the Scripture says
1
There is one God
Scripture is emphatic: 'Hear, Israel: Yahweh is our God. Yahweh is one.' God declares, 'I am Yahweh, and there is no one else.' The Bible is fiercely monotheistic: there is one God, and nothing else is to be worshipped.
Hear, Israel: Yahweh is our God. Yahweh is one.Hear, O Israel: The Lord our God is one Lord:
I am Yahweh, and there is no one else. Besides me, there is no God. I will strengthen you, though you have not known me;I am the Lord, and there is none else, there is no God beside me: I girded thee, though thou hast not known me:
Jesus answered, “The greatest is, ‘Hear, Israel, the Lord our God, the Lord is one:And Jesus answered him, The first of all the commandments is, Hear, O Israel; The Lord our God is one Lord:
The Father is God; the Son is called God: 'In the beginning was the Word, and the Word was with God, and the Word was God,' and Thomas confesses Jesus as 'My Lord and my God'; and the Spirit is God, as Peter made plain to Ananias. Three Persons, each fully divine.
In the beginning was the Word, and the Word was with God, and the Word was God.In the beginning was the Word, and the Word was with God, and the Word was God.
But Peter said, “Ananias, why has Satan filled your heart to lie to the Holy Spirit, and to keep back part of the price of the land? While you kept it, didn’t it remain your own? After it was sold, wasn’t it in your power? How is it that you have conceived this thing in your heart? You haven’t lied to men, but to God.”But Peter said, Ananias, why hath Satan filled thine heart to lie to the Holy Ghost, and to keep back part of the price of the land? Whiles it remained, was it not thine own? and after it was sold, was it not in thine own power? why hast thou conceived this thing in thine heart? thou hast not lied unto men, but unto God.
But of the Son he says, “Your throne, O God, is forever and ever. The scepter of uprightness is the scepter of your Kingdom.But unto the Son he saith, Thy throne, O God, is for ever and ever: a sceptre of righteousness is the sceptre of thy kingdom.
Yet they are distinct Persons who relate to one another
At Jesus' baptism, the Spirit descends upon the Son while the Father speaks from heaven: three Persons present at once. In the upper room, the Son asks the Father to send the Spirit. They love, send, glorify, and speak to one another.
Jesus, when he was baptized, went up directly from the water: and behold, the heavens were opened to him. He saw the Spirit of God descending as a dove, and coming on him. Behold, a voice out of the heavens said, “This is my beloved Son, with whom I am well pleased.”And Jesus, when he was baptized, went up straightway out of the water: and, lo, the heavens were opened unto him, and he saw the Spirit of God descending like a dove, and lighting upon him: And lo a voice from heaven, saying, This is my beloved Son, in whom I am well pleased.
I will pray to the Father, and he will give you another Counselor, that he may be with you forever,— the Spirit of truth, whom the world can’t receive; for it doesn’t see him, neither knows him. You know him, for he lives with you, and will be in you.And I will pray the Father, and he shall give you another Comforter, that he may abide with you for ever; Even the Spirit of truth; whom the world cannot receive, because it seeth him not, neither knoweth him: but ye know him; for he dwelleth with you, and shall be in you.
Jesus said these things, and lifting up his eyes to heaven, he said, “Father, the time has come. Glorify your Son, that your Son may also glorify you; even as you gave him authority over all flesh, he will give eternal life to all whom you have given him. This is eternal life, that they should know you, the only true God, and him whom you sent, Jesus Christ. I glorified you on the earth. I have accomplished the work which you have given me to do. Now, Father, glorify me with your own self with the glory which I had with you before the world existed.These words spake Jesus, and lifted up his eyes to heaven, and said, Father, the hour is come; glorify thy Son, that thy Son also may glorify thee: As thou hast given him power over all flesh, that he should give eternal life to as many as thou hast given him. And this is life eternal, that they might know thee the only true God, and Jesus Christ, whom thou hast sent. I have glorified thee on the earth: I have finished the work which thou gavest me to do. And now, O Father, glorify thou me with thine own self with the glory which I had with thee before the world was.
The Great Commission puts it beyond dispute: baptize 'in the name,' singular, 'of the Father and of the Son and of the Holy Spirit.' The earliest confession of the church was already trinitarian, because that is how God revealed Himself.
Go,and make disciples of all nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit,Go ye therefore, and teach all nations, baptizing them in the name of the Father, and of the Son, and of the Holy Ghost:
The grace of the Lord Jesus Christ, the love of God, and the fellowship of the Holy Spirit, be with you all. Amen.The grace of the Lord Jesus Christ, and the love of God, and the communion of the Holy Ghost, be with you all. Amen. The second epistle to the Corinthians was written from Philippi, a city of Macedonia, by Titus and Lucas.
The Father chose us and loved us before the foundation of the world; the Son redeemed us by His blood; the Spirit sealed us and dwells in us. Every blessing of salvation flows from the triune God, and we are invited into His fellowship.
Blessed be the God and Father of our Lord Jesus Christ, who has blessed us with every spiritual blessing in the heavenly places in Christ; even as he chose us in him before the foundation of the world, that we would be holy and without defect before him in love; having predestined us for adoption as children through Jesus Christ to himself, according to the good pleasure of his desire, to the praise of the glory of his grace, by which he freely bestowed favor on us in the Beloved, in whom we have our redemption through his blood, the forgiveness of our trespasses, according to the riches of his grace, which he made to abound toward us in all wisdom and prudence, making known to us the mystery of his will, according to his good pleasure which he purposed in him to an administration of the fullness of the times, to sum up all things in Christ, the things in the heavens, and the things on the earth, in him; in whom also we were assigned an inheritance, having been foreordained according to the purpose of him who works all things after the counsel of his will; to the end that we should be to the praise of his glory, we who had before hoped in Christ: in whom you also, having heard the word of the truth, the Good News of your salvation—in whom, having also believed, you were sealed with the Holy Spirit of promise, who is a pledge of our inheritance, to the redemption of God’s own possession, to the praise of his glory.Blessed be the God and Father of our Lord Jesus Christ, who hath blessed us with all spiritual blessings in heavenly places in Christ: According as he hath chosen us in him before the foundation of the world, that we should be holy and without blame before him in love: Having predestinated us unto the adoption of children by Jesus Christ to himself, according to the good pleasure of his will, To the praise of the glory of his grace, wherein he hath made us accepted in the beloved. In whom we have redemption through his blood, the forgiveness of sins, according to the riches of his grace; Wherein he hath abounded toward us in all wisdom and prudence; Having made known unto us the mystery of his will, according to his good pleasure which he hath purposed in himself: That in the dispensation of the fulness of times he might gather together in one all things in Christ, both which are in heaven, and which are on earth; even in him: In whom also we have obtained an inheritance, being predestinated according to the purpose of him who worketh all things after the counsel of his own will: That we should be to the praise of his glory, who first trusted in Christ. In whom ye also trusted, after that ye heard the word of truth, the gospel of your salvation: in whom also after that ye believed, ye were sealed with that holy Spirit of promise, Which is the earnest of our inheritance until the redemption of the purchased possession, unto the praise of his glory.
The grace of the Lord Jesus Christ, the love of God, and the fellowship of the Holy Spirit, be with you all. Amen.The grace of the Lord Jesus Christ, and the love of God, and the communion of the Holy Ghost, be with you all. Amen. The second epistle to the Corinthians was written from Philippi, a city of Macedonia, by Titus and Lucas.
Jesus answered him, “If a man loves me, he will keep my word. My Father will love him, and we will come to him, and make our home with him.Jesus answered and said unto him, If a man love me, he will keep my words: and my Father will love him, and we will come unto him, and make our abode with him.
Go,and make disciples of all nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit,Go ye therefore, and teach all nations, baptizing them in the name of the Father, and of the Son, and of the Holy Ghost:
I will pray to the Father, and he will give you another Counselor, that he may be with you forever,— the Spirit of truth, whom the world can’t receive; for it doesn’t see him, neither knows him. You know him, for he lives with you, and will be in you.And I will pray the Father, and he shall give you another Comforter, that he may abide with you for ever; Even the Spirit of truth; whom the world cannot receive, because it seeth him not, neither knoweth him: but ye know him; for he dwelleth with you, and shall be in you.
The grace of the Lord Jesus Christ, the love of God, and the fellowship of the Holy Spirit, be with you all. Amen.The grace of the Lord Jesus Christ, and the love of God, and the communion of the Holy Ghost, be with you all. Amen. The second epistle to the Corinthians was written from Philippi, a city of Macedonia, by Titus and Lucas.
His Son is the radiance of his glory, the very image of his substance, and upholding all things by the word of his power, when he had by himself purified us of our sins, sat down on the right hand of the Majesty on high;Who being the brightness of his glory, and the express image of his person, and upholding all things by the word of his power, when he had by himself purged our sins, sat down on the right hand of the Majesty on high;