First let us start with what is the trinity?It is the belief that the creator God YHVH,Jesus and the Holy Spirit are three persons of one essence and character.That God exists in three aspects in a sense or God has three persons ,it is a very abstract thing.Does one have to believe in the trinity to be saved though?Also is the trinity true doctrine,I will get to that also.

What do you have to believe to be saved first of all.

John 14:6 New International Version

⁶ Jesus answered, “I am the way and the truth and the life. No one comes to the Father except through me.

This is clear ,no one sees the Father except by the Son Jesus.However nothing here mentions a trinity explicitly nor is the trinity explicitly mentioned in the Bible in general as a concrete concept.

John 3.3

³ Jesus replied, “Very truly I tell you, no one can see the kingdom of God unless they are born again.”

Here is Romans 10.9-10

  ⁹ “If you declare with your mouth, “Jesus is Lord,” and believe in your heart that God raised him from the dead, you will be saved. ¹⁰ For it is with your heart that you believe and are justified, and it is with your mouth that you profess your faith and are saved.”

It is clear the only way to see God’s kingdom is to have your spirit renewed by being born again and declaring Jesus as the only savior is the only way to that.I think that point is clear but the trinity is not spefically mentioned really.Some things to think about though is that if Jesus is not divine and God than in John 14.6 how can he keep the gate to the Father and Romans 9 makes it clear that you must declare Jesus as Lord.So far Jesus of Nazereth seems on par with the Father which implies a trinity.Jesus is called Lord in Romans excplicitly ,and if Jesus is a created being then how can he be on par with the Lord.

What if the Jesus and the Father are the same and Jesus is purely divine and Jesus is sinply God.This is called monophysitism,but here the problem lies that without Jesus having a human nature along with a divine nature than Jesus could not have suffered and shed blood for us.It is the blood Jesus shed that saved us.

Mathew 26.28 NIV

²⁸ This is my blood of the covenant, which is poured out for many for the forgiveness of sins.

Hebrews 9.12 NIV

¹² He did not enter by means of the blood of goats and calves; but he entered the Most Holy Place once for all by his own blood, thus obtaining^[a] eternal redemption.

So the death,suffering and the blood of Jesus are most important parts to the plan of salvation and this requires a human nature and so not just the divinity but the humanity of Jesus are key.So those who deny Jesus’s human nature also deny his suffering and his suffering gives of redemption and life and healing.I think the belief that Jesus has a human side is very important.Once you fully deny the Father and make Jesus Lord without the Father that is the Gnostic and Marcion heresy which we will not go into but please to look it up and it’s dangers.I am not saying that those who believe in a purely divine Jesus are not saved,I’m not a minister or theologian,I can’t tell you that, but if you are into gnosticism you are not saved though,that I can say.It is Biblical that our salvation came from the awful suffering Jesus endured and that requires a human aspect.

What about those who believe in a purely human nature(the Arian Heresy)

Let us start with what is the Arian heresy and no it’s not about nazi’s,Arius was a Libyan or maybe Tunisian 4th century CE Greek speaking Bishop of the early church.This was before the Catholic,Eastern Orthodox and Oriental Orthodox parted ways.Arius purposed that Jesus was a fully subordinate created being and was not to be worshiped and only the Father(YHVH) should be worshiped.He was excommunicated as a heretic but a few Roman emperors embraced him along withn a lot of Gothic tribes.The most similar to Arian theology today would be the Jehovah’s witnesses and Christadelphians.However although the Bible does indicate that Jesus does lack some of the Father’s knowledge in the incarnation,most notable in Revelation where it says “only the Father knows the day of the end”.But Romans makes it clear though that Jesus is Lord from what I quoted above in this article.Also that no one will ever see the Father except by the Son and also that Jesus rose to the right hand of God.

Romans 8:34 New International Version

³⁴ Who then is the one who condemns? No one. Christ Jesus who died—more than that, who was raised to life—is at the right hand of God and is also interceding for us.

I do not believe that trivializing Jesus is wise and is counter to scripture.

Was the trinity pre cross era?In short yes ,there was a belief in two powers in heaven.For example the Priest Malkhi-Zedek or the King of Righteousness of the book of Genesis was thougt to be Jesus.There was the character Metatron from the third book of Enoch(from the Ethiopic canon) Where Enoch had a vision of the throne of God.But sitting on the throne was not YHVH himself but YHVH katan (meaning small Lord).Many believe Metatron was a metaphor for a pre cross era Jesus.The late theologian Michael Heiser thought the angel Jacob wrestled with in Genesis was really Jesus and not an angel.The two powers in heaven theory was a common belief in Judaism until the second or third century CE until the Rabbi’s felt it looked to much like Jesus and the two powers in heaven theory was called heretical.However in books like the Zohar God existing in two persons in common in jewish Kabalistic thought.You can read my article about Jesus in the Zohar in this site https://biblicalhistory9.com/2024/01/28/is-jesus-in-the-zohar/

Here is one more thing on Jesus in the Old Testament I forgot from the book of Daniel 7.13-14

¹³ “In my vision at night I looked, and there before me was one like a son of man, coming with the clouds of heaven. He approached the Ancient of Days and was led into his presence. ¹⁴ He was given authority, glory and sovereign power; all nations and peoples of every language worshiped him. His dominion is an everlasting dominion that will not pass away, and his kingdom is one that will never be destroyed.”

So a belief of God existing in two persons of one essence pre dated the incarnation of Jesus himself.

In closing I will say that although the trinity is never a theory mentioned by name in scripture it is spoken is implication and this is why it had wide belief.Do you have to believe in the trinity technically to be saved? No ,but many of the core tenents of salvation if you think about them strongly suggest a trinity.The trinity is less a concrete theory but an abstract understanding of an ineffable Godhead to awesome for technical description.

Thank you and God Bless and put all question in the comments.