2Timothy2:19 *"Nevertheless, God’s solid foundation stands firm, sealed with this inscription: “The Lord knows those who are his,” and, “Everyone who confesses the name of the Lord must turn away from wickedness*”.
There are fundamental doctrines( teachings) of the Christian faith that are non-negotiable. If any church or acclaimed believer refutes any of them, they are not one of us.
The fundamental doctrines of our faith can be likened to the pillars holding a house intact. The colour of the house, front design, and roof type may be different but these pillars are the essentials which If removed, the house collapses.
Before you call anyone "brother" or "sister" in Christ, they must agree on these things. What we know today as fundamental doctrines were settled by church fathers between 325- 451 AD because of the several heresies trying to find its way into mainstream christianity.
I.*DOCTRINE OF TRINITY*
Our faith is trinitarian. When we say 'Trinity', what do we mean and what are the implications of not accepting this doctrine?
The word trinity itself is not in the bible but the concept is right there from Genesis to revelation. *Trinity simply means one God in three distinct co-equal persons: Father, Son, Holy Spirit. That is, we have one God existing in three distinct persons*. Let's examine scriptures.
Matthew 28:19: *"Go therefore and make disciples of all nations, baptizing them in the name of the FATHER and of the SON and of the HOLY SPIRIT*".
So, when we baptize people in water, we do it in the name of the holy trinity as commanded by Jesus Himself. When we share the grace in church, we affirm the holy trinity. That is exactly what we do in our meetings.
2 Corinthians 13:14: *"The grace of the Lord JESUS CHRIST and the love of GOD(the father) and the fellowship of the HOLY SPIRIT be with you all*".
When Jesus was baptized, three distinct personalities were revealed to us yet they are one.
Matthew 3: 16 says, *"After his baptism, as Jesus (God the Son) came up out of the water, the heavens were opened and he saw the Spirit of GOD (the Spirit) descending like a dove and settling on him. [17] And a voice (the father) from heaven said, “This is my dearly loved Son, who brings me great joy*”( Emphasis mine).
God the father spoke from heaven, God the son was baptized in water and God the Holy Spirit rested on the Son like a dove.
This is not three gods as some posit neither is it one person existing in three forms/ modes. I have heard some preachers say, God the father turned to God the son and God the son transformed into God the Holy Spirit. That is modalism, that is not trinity. The bible did not teach that.
Trinity is not God manifesting in three modes, rather it is one God existing in three distinct co-equal persons. This is a mystery revealed in scriptures. This establishes that the Christian faith is monotheistic yet trinitarian and not polytheistic.
1 Timothy 2:5: *"For there is ONE GOD and one mediator between God and mankind, the man Christ Jesus*".
Deuteronomy 6:4: *"Hear, O Israel: The LORD our God, the LORD IS ONE!*"
In a nutshell, as Christians, we believe in One God (monotheism) who exists in three(trinitarinism) persons: Father, Son and Holy Spirit. That is what we call trinity.
The Jehovah Witnesses, Mormons, and other sects with similar beliefs are not your brother in Christ because they deny this fundamental truth.