We must believe:
1. In the Trinity (the Father, the Son, and the Holy Spirit)
(i.e. God exists as three distinct persons and yet He is one God or being).
Scriptural support for the Trinity:
1 John 5:7 (KJV) says,
"For there are three that bear record in heaven, the Father, the Word, and the Holy Ghost: and these three are one."
The Bible teaches that there is one God (Deuteronomy 6:4) (1 Timothy 2:5) (Isaiah 45:5).
Yet, the Bible also teaches that there are distinctions within the Godhead or that there is a plural nature to God.
Here are a couple of quick points:
#1. The word Elohim (אֱלֹהִ֔ים) is both a singular and a plural noun.
#2. God refers to Himself in plural form (
Genesis 1:26) (
Genesis 3:22) (
Genesis 11:7) (
Isaiah 6:8).
#3. Plurality of God in New Testament (
Matthew 28:19) (
2 Corinthians 13:14) (
John 14:16-20).
#4. Introductions to both the Son & Holy Spirit (
Daniel 7:9,
10,
13,
14) (
John 14:16)
#5. Different persons of Godhead appear at one time (
Luke 3:21-22)
#6. Distinctions of Wills (
Luke 22:42).
#7. Conversations Between the Godhead (
Psalm 2:1-12) (
Psalm 45:6-7) (
Psalm 110:1) (
Matthew 11:27) (
John 17:24).
Is not believing in the Trinity a salvation issue?
Jesus says to whom much is given, much is required (Luke 12:48).
I believe that a person will not be held guilty for something they do not know about. For we know God is fair and just. So a new believer (who does not know about the Trinity) is most likely not going to be condemned for not knowing the entire truth about God yet. But in time, when they learn of the Trinity by Scripture, and they reject that truth, I believe then it would be a salvation issue (i.e. a loss of salvation for them).
How so?
Jesus says,
"God is a Spirit: and they that worship him
must worship him in spirit and in truth." (John 4:24).
God will turn against anyone who worships a false god.
"If any of you worship Molech, I will turn against you and your entire family, and I will no longer let you belong to my people." (Leviticus 20:5).
"He that sacrificeth unto any god, save unto the LORD only, he shall be utterly destroyed." (Exodus 22:20).
If one knows of the Trinity, and they reject it: Then worshiping anything other god besides the Trinity is worship of a false god.
We can see in Leviticus 20:5, Exodus 22:20 that God will not stand for false worship of another god.
Note: I am not saying a person can worship Molech in ignorance and be saved. I am only saying that this is the case with a new believer who does not have knowledge of the Trinity so far, and yet they believe in Jesus as their Lord and Savior.
We also know God will not accept us changing the truth of God into a lie, either.
Romans 1:25 says,
"Who changed the truth of God into a lie, and worshipped and served the creature more than the Creator,..."
Romans 1:26 says,
"For this cause God gave them up unto vile affections..."
Romans 1:21-22 says,
21 "Because that, when they knew God, they glorified him not as God, neither were thankful; but became vain in their imaginations, and their foolish heart was darkened.
22 Professing themselves to be wise, they became fools,"
(Romans 1:21-22).
Surely this is not good if a person changes the truth of God into a lie. The truth of God on the Trinity is revealed in Scripture. If a person changes this truth of God into a lie, it surely is not good or acceptable to the Lord our God (Who is one God and yet three persons, -
1 John 5:7 KJV).