If you would like to read my views on religion and how we got started with the ministry, you can read this.
According to orthodox Trinitarian doctrine, if a person claims to be a Christian but does not believe in the Trinity, he is not saved.  Is that the truth? Not from the evidence in the Bible. In fact, the evidence in Scripture is that a person can be saved without even knowing about the Trinity. Before we discuss the issue further, however, we need to know the definition of the Trinity according to orthodox theologians. This is important because some Christians think they are Trinitarians simply because they believe in the Father, the Son, and a being called “the Holy Spirit.” But that is not the Trinity. The doctrine of the Trinity is that the Father is God, the Son is God, the Holy Spirit is God, and together these “three Persons” make one God; and these three are co-equal and co-eternal, the Son having been “eternally begotten” of the Father, and Jesus being simultaneously 100% God and 100% man.
We of Spirit & Truth Fellowship International have encountered Trinitarians who say that a person will be saved if he believes that Jesus is both 100% God and 100% man, even if he does not believe the full doctrine of the Trinity. First, that is not the doctrinal position of the Orthodox Church, and second, the Bible never says that believing Jesus is both 100% God and 100% man is necessary for salvation. Non-Trinitarians assert that a person can be saved without believing in the Trinity, and demand, as did Martin Luther during the Reformation, that we be convinced from Scripture that what Trinitarians teach is true. Perhaps a good question to begin this study is, “When did God start requiring that a person believe in the Trinity to be saved?”
The Old Testament
The Old Testament does not teach the Trinity, or even set forth clearly that the Messiah would be God. Therefore it is unreasonable to think that someone back then had to believe it to be saved.  There is no evidence of anyone knowing about, or believing in, the Trinity in all the Jewish literature before Christ, including the Old Testament, the Jewish targums and commentaries, the Apocrypha or other apocryphal literature, or the Dead Sea Scrolls.
It is well known that the foundational tenet of the Old Testament faith was, “Hear, O Israel: The LORD our God is one LORD” (Deut. 6:4 – KJV), and the Jews fiercely defended that faith against polytheism of all kinds. There are some singular verses that many Trinitarians today say point to the doctrine of the Trinity underlying the revelation of the Old Testament, but none expound it clearly enough that anyone would have formulated the doctrine of a Triune God from them, and there is no historical record that anyone did (which is good evidence for the validity of our point that all those verses have a non-Trinitarian explanation).
Some Trinitarian scholars are aware of the fact that the Old Testament does not teach the Trinity. The distinguished Trinitarian scholar Bertrand de Margerie writes:
“…contemporary exegetes [Bible teachers] affirm unanimously that the Old Testament did not bring to the Jewish people a clear and distinct Revelation of the existence of a plurality of persons in God. In this they agree with the clear and frequent affirmation of Fathers such as Irenaeus, Hilary, and Gregory of Nazianzus: that the doctrine of the Trinity is revealed only in the New Testament.” 
Since many Trinitarians admit that the Trinity is not revealed in the Old Testament, there are both Trinitarians and non-Trinitarians who agree that before Jesus’ ministry a person did not have to believe in the Trinity to be saved.
The Four Gospels
We have seen that both Trinitarians and non-Trinitarians agree that a person living during the Old Testament did not have to believe in the Trinity to be saved because there was no presentation of the Trinity in the Old Testament for them to believe. However, orthodox Trinitarian doctrine is that during the ministry of Jesus, and afterward, a person had to believe in the Trinity to be saved. This means that if Jesus or the Apostles wanted anyone to be saved, they had to teach the person more information than was revealed in the Old Testament. If the orthodox Trinitarian doctrine is correct, then we should see a clear presentation of the Trinity in Scripture, but we do not, nor is there any record that Jesus, or anyone else, ever taught the doctrine of the Trinity to anyone in order to get him or her saved.
To know what people during the time of Jesus had to do to be saved, all we have to do is read the Gospels. Before we go any further, however, it is helpful to understand what the Jews at the time of Jesus were expecting about their Messiah. Some of their expectations were correct, and some were incorrect. Some of their correct expectations were that, the Messiah was going to be a human empowered by God. He would be from the line of Abraham (Gen. 22:18), from the tribe of Judah (Gen. 49:10), a descendant of David (2 Sam. 7:12 and 13), a Lord under Yahweh, the God of Israel (Ps. 110:1),  and he was to be one of their own people: “Their leader will be one of their own; their ruler will arise from among them…” (Jer. 30:21). They were also correct in that they were not expecting their Messiah to be a “God-man,” a “Person” of the Godhead, or a part of a Triune God. The first-century Jews were incorrect in not expecting their Messiah to be born of a virgin, which is why the angel had to instruct Mary about it (Luke 1:34 and 35). They were also incorrect in thinking the Messiah would not die (Matt. 16:21 and 22; John 12:32-34).
When it came to the first century Jews not expecting the Messiah to die, Jesus worked very hard to correct that misunderstanding, teaching over and over that he must die (Matt. 16:21, 17:9, 20:19 and 28, 26:2, 12 and 27-32). But there is not one single account of Jesus correcting anyone’s belief that he was a fully human Messiah. Never did he say he was part of the Trinity, or that a person had to believe in the Trinity to be saved. Furthermore, the first century Jews believed that “the Spirit of God” or “the Holy Spirit” was not a separate Person in the Trinity, but was another name for God, just as Yahweh, Elohim, or El Shaddai, were other names for the one true God. When Genesis 1:2 mentions “the Spirit of God,” Jews correctly believed it was another name for God or a reference to His invisible power at work. Yet there is no record of Jesus ever trying to “correct” them and show that the Holy Spirit was a third Person in the Trinity. That is very solid evidence that they did not have to believe in the Trinity to be saved.
If Jesus had taught that a person had to believe in the Trinity to be saved, the perfect time for him to have done so would have been when a young man came to him and asked, “…Teacher, what good thing must I do to get eternal life?” (Matt. 19:16). If this young man had to believe in the Trinity to be saved, this was the time to say so. Instead, Jesus said, “…If you want to enter life, obey the commandments” (Matt. 19:17). Jesus further instructed the man that if he wanted to be “perfect” (which Mark 10:21 equates as having treasure in heaven) he should sell his worldly possessions and follow him (Matt. 19:21). Jesus never said to the man that belief in any aspect of the Trinity was necessary for salvation.
Another time Jesus could have easily taught the Trinity, or even that he was God, was when he traveled through Samaria, the district north of Jerusalem and south of Galilee. The Samaritans were not Jews, but foreigners who had been brought into the area and had adopted some parts of the Jewish religion. The Jews regarded them as horrible pagans and pretenders, and had nothing to do with them. When Jesus met the woman at the well in Samaria, she said she knew the Messiah was coming (John 4:25). However, her understanding of the Messiah would have come from the Old Testament and what her tradition taught, so when Jesus said, “…I who speak to you am he” (John 4:26), she never would have concluded that he was somehow God, or part of a Triune God. If she needed to believe that to be saved, Jesus would have taught it to her, as well as to the people from Samaria who came to meet him after the woman told them about him (John 4:41). However, there is no hint in Scripture he ever mentioned the Trinity. Did he ignore their need for salvation? Of course not. What is evident from this record is that a person did not have to believe in the Trinity to be saved.
Another example of a person being saved without believing in the Trinity is the immoral woman who anointed Jesus’ feet with her tears while he was eating. All Jesus said to her was, “…Your sins are forgiven” and “…Your faith has saved you; go in peace” (Luke 7:48 and 50). Are we to believe that somehow this Galilean Jewess knew that Jesus was part of a Triune God, and by knowing that she gained salvation? Such an assumption would be to stretch the record beyond credible limits. The woman was a sinner, not a theologian, and if she went to synagogue at all, which is questionable, she would have known about the Messiah only from what the Old Testament taught. There is no reason to believe that she somehow pasted together statements Jesus had made to build a case for the Trinity, and then believed it. She, like millions of Old Testament believers before her, was saved without believing in the Trinity.
Theologians build the doctrine of the Trinity with verses pulled from all over the Bible, but only a few actually spoken by Jesus can even be used to support it, and none of those mention “the Holy Spirit” in any decisive sense as being a distinct “Person.”  Furthermore, each statement Jesus made that modern Trinitarians use to paste together their case for a Trinity has an alternative, non-Trinitarian explanation. This is important, because although a person who already believes in the Trinity might think that what Jesus said supported the doctrine of the Trinity, someone who never heard of the Trinity would understand what Jesus said in a totally different way.
A good example of this was when Jesus said, “…if you do not believe that I am the one I claim to be, you will indeed die in your sins” (John 8:24). Some Trinitarians see this statement as supporting the Trinity, but someone who did not know that doctrine would understand the statement in light of what he knew and believed, especially if what Jesus said made sense in terms of the beliefs he already held. In the case of John 8:24, the Jews he was speaking to were expecting a human Messiah and that people who rejected him would die in their sins. What Jesus said fit their understanding perfectly. Jesus had to have known that, so if he was trying to say that anyone who did not believe in the Trinity was unsaved, he did a poor job of making his point. He certainly never stated that if someone does not believe in the Trinity, he would die in his sins.
If a person did need to believe in the Trinity to be saved, we would expect that Jesus would have been at least as aggressive in teaching that as he was about correcting other erroneous beliefs of his day. For example, we mentioned earlier that Jesus plainly taught his disciples that he had to die, even though they were not expecting it. He also corrected the Sadducees concerning the resurrection very plainly, telling them, “You are in error” (Matt. 22:29). Time after time he openly corrected the errors believed by the people around him. In the Sermon on the Mount he corrected many erroneous teachings, including the people’s misunderstanding about love, revenge, adultery, divorce, and anger, often saying, “You have heard that it was said…But I tell you…” (Matt. 5:21-44). But never in that important teaching that spans three entire chapters in Matthew does he correct their ideas about him being a real human being, or teach them about the Trinity, which he would have if it was necessary for people to believe that to be saved. After all, which is the more important theological mistake, being wrong about anger, taking an oath, and praying in public, or being wrong about the true nature of God?
If the Trinity were a true doctrine, and especially if a person has to believe it to be saved, we would have expected Jesus to say something in the Sermon on the Mount such as this:
“You have heard that it was said” that God is One, “but I tell you” that God is a Trinity, one God made of three distinct Persons.  “You have heard that it was said” that the Messiah will be one from among you, “but I tell you” he will be more than that, he will be God incarnated in human flesh. “You have heard that it was said” that the holy spirit is the invisible spirit power of God, “but I tell you” that Holy Spirit is much more than that, he is the third Person in a Triune Godhead.”
Are we to believe that Jesus openly and plainly corrected errors in people’s understanding about many different issues while never correcting people’s erroneous thinking that he was the human Messiah they expected, and not a “Person” in a Triune God, especially if their error meant they were not saved? That makes no sense. He did not even correct his closest disciples about the Trinity. When Jesus asked Peter, “…Who do you say I am?” (Matt. 16:15), …Peter answered, “You are the Christ, the Son of the Living God” (Matt. 16:16). Peter believed Jesus was the Christ he had been taught about in synagogue and was expecting, not that he was God in the flesh who was part of the Trinity. Yet Jesus did not correct Peter, but instead complimented him on his insight, saying he was “Blessed” (Matt. 16:17).
Jesus never taught the doctrine of the Trinity or told anyone he had to believe it to be saved. Furthermore, he never corrected anyone’s belief that he was the human Messiah they expected and not part of a Triune God. When he taught about himself from the Old Testament, as he did in Nazareth when he quoted from Isaiah (Luke 4:18 and 19), he never even hinted that there was more to believe about him than the Old Testament scriptures taught. Nor did he ever correct anyone’s understanding about the Holy Spirit. All this is conclusive evidence that Jesus did not teach that a person had to believe in the Trinity to be saved.
The Book of Acts
The book of Acts records the teachings of the Apostles and disciples as they spread the good news of Jesus. It is reasonable that if the doctrine of the Trinity were a truth not revealed in the Old Testament but necessary for Christian salvation, it should be clearly taught in Acts. After all, many Trinitarians believe that for an unbelieving Jew or pagan Gentile to be saved, he must believe in the Trinity. The book of Acts, then, is a proving ground for what unbelievers need to know in order to be saved. So what do we see in Acts? In all the sermons in the book of Acts there is not one presentation of the Trinity.
What Acts does record very clearly is that Jesus was a man, the servant of God, who was God’s anointed (“Messiah” in Hebrew, “Christ” in Greek), who died, whom God raised from the dead and exalted, and who will be the future King and Judge of all mankind. Furthermore, those who hear and believe that message get saved without hearing anything about the Trinity. Time after time Paul and others went into Jewish Synagogues and taught from the Old Testament about the Messiah, explaining that Jesus was the Messiah the Old Testament spoke of, and that teaching was enough to get people saved. There is not one record of Paul or others saying that what the Old Testament taught about the Messiah was not enough for salvation.
Thanks for reading.
(Comments have been turned off. The information is here to inform and bless you. God granted you the gift of free will – take it or leave it).