On the doctrine of Trinity
The term “Trinity” (or Triunity) has never appeared in the Bible, but it does not necessarily mean that it is unbiblical. As a matter of fact, it is a foundational doctrine for Christian faith. Whether accept or deny this doctrine, is the distinguishing mark between the orthodoxy and heresy.
Trinity the definition:
“God eternally exists as three Persons, Father, Son and Holy Spirit, and each Person is fully God, and there is one God.” (Wayne Grudem)
“There is one only and true God, but in the unity of the Godhead there are three coeternal and coequal Persons, the same in substance but distinct in subsistence.” (B. B. Warfield)
I. The concept in the Old Testament
A. The Unity of God
“Hear, O Israel: The LORD our God, the LORD is one. Love the LORD your God with all your heart and with all your soul and with all your strength. These commandments that I give you today are to be on your hearts. Impress them on your children. Talk about them when you sit at home and when you walk along the road, when you lie down and when you get up. Tie them as symbols on your hands and bind them on your foreheads. Write them on the doorframes of your houses and on your gates.” (Deut 6:4-9)
“Hear, O Israel: The LORD our God, the LORD is one.” (Deut 6:4)
“Remember the former things, those of long ago; I am God, and there is no other; I am God, and there is none like me.” (Isa 46:9)
B. The plural form expressions
“Then God said, "Let us make man in our image, in our likeness.” (Gen 1:26)
“(The LORD said), Come, let us go down and confuse their language so they will not understand each other." (Gen 11:7)
“Then I heard the voice of the Lord saying, ‘Whom shall I send? And who will go for us?’" (Isa 6:8)
“Your throne, O God, will last for ever and ever; a scepter of justice will be the scepter of your kingdom. You love righteousness and hate wickedness; therefore God, your God, has set you above your companions by anointing you with the oil of joy.” (Ps 45:6-7)
The author did not talk to any human king, but to “God” whose throne will endure forever and ever, he said, “Your God, has set you above your companions,” obviously there are two persons are to be called “God.” (in the New Testament, the author of Hebrews applied Him to be Christ. [Heb 1:8])
“The LORD says to my Lord: ‘Sit at my right hand until I make your enemies a footstool for your feet.’"(Ps 110:1)
There are two Lords here, and who can sit at the right hand of God but God Himself?
“Then the LORD rained down burning sulfur on Sodom and Gomorrah--from the LORD out of the heavens.” (Gen 19:24)
Again, there are two LORDs here, one is in heaven, one is on earth.
“‘The Redeemer will come to Zion, to those in Jacob who repent of their sins,’ declares the LORD. ‘As for me, this is my covenant with them,’ says the LORD. ‘My Spirit, who is on you, will not depart from you.’” (Isa 59:20-21)
Notice that the Lord, the Redeemer, the Spirit of the Lord, all divine Godhead appeared here in this passage.
“The Spirit of the Sovereign LORD is on me.” (Isa 61:1) (Note that three persons appeared in this verse)
“Yet they rebelled and grieved his Holy Spirit.” (Isa 63:10)
“And now the Sovereign LORD has sent me, with his Spirit.” (Isa 48:16)
C. The Angel of the Lord
The “Angel” (The Messenger) of the Lord is distinct from the Lord Himself, yet the Angel of the Lord sometimes is called “God” or “the Lord.”
“The angel of the LORD found Hagar near a spring in the desert; ...She (Hagar) gave this name to the LORD who spoke to her: ‘You are the God who sees me.’”(Gen 16:7; 13)
“There the angel of the LORD appeared to him in flames of fire from within a bush. Moses saw that though the bush was on fire it did not burn up. ... So Moses thought, ‘I will go over and see this strange sight--why the bush does not burn up.’ When the LORD saw that he had gone over to look, God called to him from within the bush, ‘Moses! Moses!’ And Moses said, ‘Here I am.’ ‘Do not come any closer,’ God said. ‘Take off your sandals, for the place where you are standing is holy ground.’ Then He said, ‘I am the God of your father, the God of Abraham, the God of Isaac and the God of Jacob.’ At this, Moses hid his face, because he was afraid to look at God.” (Exod 3:2-6)
“When the angel of the LORD appeared to Gideon, he said, ‘the LORD is with you, mighty warrior.’”
II. The Trinity in the New Testament
A. The Oneness of God
Like the Old Testament, the New Testament also insists that there is only one true God.
“Yet for us there is but one God, the Father, from whom all things came and for whom we live.” (1 Cor 8:6)
“For there is one God and one mediator between God and men, the man Christ Jesus.” (1 Tim 2:5)
“You believe that there is one God. Good! Even the demons believe that--and shudder.” (James 2:19)
B. Three Persons of the Godhead
There are passages that the three Persons of the Trinity are mentioned together in the New Testament.
“As soon as Jesus was baptized, He went up out of the water. At that moment heaven was opened, and He saw the Spirit of God descending like a dove and lighting on Him. And a voice from heaven said, ‘This is my Son, whom I love; with Him I am well pleased.’"(Matt 3:16-17)
“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.” (Matt 28:19)
Note that the Name is singular, yet the Three persons of the Godhead are under the same Name.
“And I will ask the Father, and He will give you another Counselor to be with you forever. ...But the Counselor, the Holy Spirit, whom the Father will send in my name, will teach you all things and will remind you of everything I have said to you.” (John 14:16; 26)
In this passage, the Holy Spirit, God the Father, and Jesus Christ, they are distinct three Persons of the Godhead.
“There are different kinds of gifts, but the same Spirit. There are different kinds of service, but the same Lord. There are different kinds of working, but the same God works all of them in all men.” (1 Cor 12:4-6)
“May the grace of the Lord Jesus Christ, and the love of God, and the fellowship of the Holy Spirit be with you all.” (2 Cor 13:14)
This is the Trinitarian expression in the apostolic blessing.
“There is one body and one Spirit--just as you were called to one hope when you were called--one Lord, one faith, one baptism; one God and Father of all, who is over all and through all and in all.” (Eph 4:4-6)
“(God’s elect,) who have been chosen according to the foreknowledge of God the Father, through the sanctifying work of the Spirit, for obedience to Jesus Christ and sprinkling by his blood: Grace and peace be yours in abundance.” (1 Pet 1:2)
C. Each Person of the Trinity is fully God
1. The Father is God
“In the beginning God created the heavens and the earth.” (Gen 1:1)
“Do not work for food that spoils, but for food that endures to eternal life, which the Son of Man will give you. On Him God the Father has placed His seal of approval." (John 6:27)
Father is the One to whom Jesus prays always.
“Father, the time has come. Glorify your Son, that your Son may glorify you.” (John 17:1)
“To all in Rome who are loved by God and called to be saints: Grace and peace to you from God our Father and from the Lord Jesus Christ.” (Rom 1:7)
“Who have been chosen according to the foreknowledge of God the Father, through the sanctifying work of the Spirit, for obedience to Jesus Christ and sprinkling by his blood: Grace and peace be yours in abundance.” (1 Pet 1:2)
2. Jesus Christ is God
“In the beginning was the Word, and the Word was with God, and the Word was God.” (John 1:1)
The Word here clearly refers to Jesus Christ (John 1:14) and He was with God and He was God in the very beginning.
“‘I tell you the truth,’ Jesus answered, ‘before Abraham was born, I am!’” (John 8:58)
Note that “I Am” was the Name of God in Ole Testament (Exod 3:14), and Jesus applied this Title to Himself.
“Thomas said to Him, ‘My Lord and my God!’” (John 20:28)
“For to us a Child is born, to us a Son is given, and the government will be on His shoulders. And He will be called Wonderful, Counselor, Mighty God, Everlasting Father, Prince of Peace.” (Isa 9:6)
This was the most famous prophecy concerning the Messiah in the Old Testament, it refers the Messiah (Jesus Christ) as almighty God.
“The virgin will be with child and will give birth to a Son, and will call Him Immanuel.” (Isa 7:14)
This well-known verse gave the Son the Name Immanuel, which means God with us.
“A voice of one calling: ‘In the desert prepare the way for the LORD; make straight in the wilderness a highway for our God.’” (Isa 40:3)
This OT prophecy was about John the Baptist’s preparing the way for Jesus Christ, who was called the Lord and our God.
“Theirs are the patriarchs, and from them is traced the human ancestry of Christ, who is God over all, forever praised! Amen.” (Rom 9:5)
“While we wait for the blessed hope--the glorious appearing of our great God and Savior, Jesus Christ.” (Titus 2:13)
“The Son is the radiance of God's glory and the exact representation of his being, sustaining all things by his powerful word.” (Heb 1:3)
“But about the Son He says, ‘Your throne, O God, will last for ever and ever, and righteousness will be the scepter of your kingdom. ... He also says, ‘In the beginning, O Lord, You laid the foundations of the earth, and the heavens are the work of Your hands.’” (Heb 1:8;10)
“Simon Peter, a servant and apostle of Jesus Christ, to those who through the righteousness of our God and Savior Jesus Christ have received a faith as precious as ours.” (2 Pet 1:1)
Jesus Himself claimed attributes which only God possesses, like Omniscience (Matt 9:4), Omnipotence (Matt 28:18), Omnipresence (Matt 28:20). He did things only God can do, such as forgiving sins (Mark 2:1-12), and raising the dead (John 11:43), upholding all things (Col 1:17; Heb 1:3), Creating all things (Col 1:16), judging of all (John 5:27), etc.
3. The Holy Spirit is God
“Then Peter said, ‘Ananias, how is it that Satan has so filled your heart that you have lied to the Holy Spirit ...? ...You have not lied to men but to God." (Acts 5:3-4)
“Now the Lord is the Spirit, and where the Spirit of the Lord is, there is freedom.” (2 Cor 3:17)
“Don't you know that you yourselves are God's temple and that God's Spirit lives in you?” (1 Cor 3:16)
This passage indicates that God’s Spirit equal with God Himself.
“Where can I go from your Spirit? Where can I flee from your presence? If I go up to the heavens, you are there; if I make my bed in the depths, you are there.” (Ps 139:7-8) (Omnipresence)
“Do you not know that your body is a temple of the Holy Spirit?” (1 Cor 6:19) (Omnipresence)
“but God has revealed it to us by his Spirit. The Spirit searches all things, even the deep things of God.” (1 Cor 2:10) (Omniscience)
“But you will receive power when the Holy Spirit comes on you; and you will be my witnesses in Jerusalem, and in all Judea and Samaria, and to the ends of the earth.” (Acts 1:8) (Omnipotence)
“Jesus answered, "I tell you the truth, no one can enter the kingdom of God unless he is born of water and the Spirit. Flesh gives birth to flesh, but the Spirit gives birth to spirit.” (John 3:5-6) (Regeneration)
In Matt 28:19, The Holy Spirit is classified on an equal level with the Father and the Son.
In John 14:26, The Holy Spirit is considered as another Counselor, same qualification as the Son.
The same patterns appeared in the following passages:
1 Cor 12:4-6; 2 Cor 13:14; Eph 4:4-6; 1 Pet 1:2; Jude 20-21.
In the passages such as Acts 28:25-27 and Heb 3:7-11, the Lord’s sayings in the OT are credited to the Holy Spirit.
Holy, holy, holy! Lord God Almighty!
Early in the morning our song shall rise to Thee;
Holy, holy, holy, merciful and mighty!
God in three Persons, blessed Trinity!