The very beginnings of Christianity are recorded in The Bible (specifically the New Testament):
Christianity was founded by Jesus Christ: the prophesied Messiah that would save his people (Israel) from their sins.
He became a “Rabbi” in Galilee (The Hebrew word for ‘teacher’: usually a title given to a man that was a Jewish Tanakh scholar [The Tanakh was the Jewish scriptures or basically the Bible’s Old Testament[1]] that was consider close to God and living a Godly life that usually lead a group of Jewish teenage boys to follow him everywhere he went in order to learn how to obey God through his example [2]) and choose 12 Jewish young men to be his disciples and taught them everything about the Torah (The Biblical Old Testament) as well as teaching them truths of God, the world, and the importance of trying to live like him because he is the son of God and Messiah:
As he was teaching his disciples truth from their scriptures as well as the basics of the Gospel/Christianity he warned them that other humans would try to deceive them/others (and succeed in deceiving many others too) and commanded then to resist deception that contradicted what he was teaching them as truth:
Matthew 24:4-5
“make sure that no one deceives you. because many will come… and will deceive many...”
He also taught many other people along with his chosen main 12 disciples and did many miracles for them: this led to many more people becoming his disciples besides his 12 main disciples:
Jews of many different ages and even women became his disciples during his 3- and 1/2-year ministry as a rabbi: after this time, he was killed. but 3 days later came back to life by his own power and told his main 12 disciples to go tell others the gospel and make more disciples just like them:
Matthew 28:19-20
“...go and make disciples…, baptizing them…, and teaching them to obey everything I have commanded you.”
So, After Jesus went back to heaven to rule with God, his original disciples that followed him during his 3- and 1/2-year ministry (including his main 12 disciples) began to tell others about the gospel and made others who believed his disciples too.[3]
Eventually an area (mostly cities) would have a large enough group of Jesus’s disciples that they would form a local group within the area where they would plan to meet together, visit one another, and learn from local teachers/preachers.
These disciples of Jesus (new and original) eventually became known as ‘Christians’ (a word that means “Christ-like”) and their local groups became the very first Churches:
The very first Churches were strictly taught only by one or more of the original disciples of Jesus (who only taught what they were in turn taught by Jesus himself and as well as what the holy scriptures said [that is the Jewish Tanakh or the later Bible’s Old Testament]).
The main 12 disciples/Jesus’s other followers constantly taught these individual churches what they previously were taught by both Jesus, his holy spirit in them, and the Tanakh/Old Testament.
These early churches were almost completely united in common beliefs and ways of living because they were taught almost the exact same thing from these disciples/followers:
So, around the very Beginning or the church (that would be around 30 A.D. to around 100 A.D.) there was mainly only one denomination:
And That was the original (Biblical) denomination of Christianity founded by the Disciples of Jesus (called Apostles) also sometimes known as Apostolic Christianity because it was started by the apostles of Jesus and their teachings.
In fact, the only division the main early church had was geographical division (churches were named after the city/place they were located in) like the church of Galatia (named after the roman region Galatia) The church of Corinth (named after the Greek city of Corinth) the church of Jerusalem (named after the city Jerusalem).
So, you would think will all this unity with the beginning of Christianity that there would be no other Christian denominations.
However
even the beginnings of the early church that was directly led by the original disciples/followers of Jesus was not without any denominational division:
Even at the very start of Christianity there were small divisions from the main group of believers in the church:
These small groups were started by individuals that were either originally Christians or heard about the Gospel/Tanakh from Jesus’s original disciples and wanted to either become famous and/or did not completely believe or live like the apostles taught and Jesus/God desired.
So, they began leading their own groups of disciples by teaching that there was a “secret” meaning of the gospels/tanakh or a “truer” way a Christian should live that the main church/disciples were not teaching. So, they got their own followers from Christians in the original church they deceived and from new pagan converts to their version of ‘Christianity’.
Some of these false beliefs that developed in the very first Churches was Nicolaism (the Biblical Belief’s/example of Bishop Nicolas [An originally ordained Church leader by one of the original 12 disciples as recorded in Acts 6:5]) and Simonianism (the Biblical Belief’s/example of Simon the Magician [A so-called ‘Christian’ who heard and believed the Gospel and was also baptized through the original disciple Phillip as recorded in Acts 8:9-25])[4]:
These people were ultimately causing division in the church and even worse the original teaching of the disciples to become distorted!
Many Christians in these new churches were already beginning to believe these false teachers and their truths they taught, and this was beginning to distort/pervert the truth’s/teaching the disciples originally taught!
Paul notes one of his churches he was responsible for (specifically the church of Galatia he had just help to establish not too long ago) was already beginning to fall into mass deception into believing ‘a false gospel’ because of these false teachers:
Galatians 1:6
“I am astonished that you are so quickly deserting the one who called you to live in the grace of Christ and are turning to a different gospel— which is really no gospel at all. Evidently some people are throwing you into confusion and are trying to pervert the gospel of Christ.”
He later asks them in anger:
Galatians 3:1
“You foolish Galatians! Who has bewitched (cast a spell on you) you?”
The fight to keep true Christianity begins!
So, almost as soon as the original churches were being established and this true Biblical/apostolic denomination of Christianity was being taught by the disciples, these deceptive ‘Christian’ teachers began to come into these churches and tried to deceive these new Christians into their distorted version of Christianity!
So not only did the disciples try to complete their mission to make new disciples of Jesus out of Judaizers and Pagans, but at the same time they also had to fight to keep the new Christians from believing these false ‘Christian’ teachers and their beliefs!
So,the Disciples openly warned about these people and told these original churches to NOT follow them but to stay with the original believes/doctrines they were originally taught by the disciples. They warned the early churches to avoided division and stay unified:
1 Corinthians 15:58
“...my dear brothers and sisters, stand firm [in what you have been taught]. Let nothing move you [from it].”
Jude 1:3
"...I felt compelled to...urge you to contend for the faith (the belief they were originally taught) that was once for all entrusted to God’s holy people (the Church: Christians)."
In fact, they said if ANYONE taught them anything else besides the original gospel truth of the scriptures/way of life they originally taught them (what Paul calls ‘another gospel’) even if IT WAS THE VERY DISCIPLES THEMSELVES teaching them this different gospel, they were to be rejected from the church as false teachers and men that were cursed by God!
Galatians 1:8-9
“…even if we [the disciples/apostles of Jesus] or an angel from heaven should preach a gospel other than the one we preached to you, let them be under God’s curse! As we have already said, so now I say again: If anybody is preaching to you a gospel other than what you accepted, let them be under God’s curse!”
Those are some very strong words not to be taken lightly!
It’s obviously not a very light thing to God for someone to come into his churches and to teach a different truth (false deception) to his people: he takes teaching a different truth that he did not tell his old prophets,Jesus,or his disciples to teach VERY SERIOUSLY!
And Paul (one of the original apostles of Jesus) wanted churches to take these false teachings equally as serious as God did!
Jesus even said himself, to his disciple John in a vision that he hated the practice of these deceptive false Christians and those who choose to follow them in their false beliefs/way of life (in this example he specifically says he hates the beliefs/ways of living of the Nicolaitans):
Revelation 2:6
“...you have this in your favor: You hate the practices of the Nicolaitans, which I also hate.”
Revelation 2:15
“Likewise, you also have those who hold to the teaching of the Nicolaitans.”
For Jesus: the founder of Christianity, to say he hated this false ‘Christianity’ is a very big deal too!
But despite all their warnings the disciples gave the churches to what Christians choose to remain loyal to Jesus and their original teachings, they were still afraid that Satan would somehow deceive the rest of them that wanted to remain loyal to Jesus.
Paul promised Jesus that he would teach and train the new Christians to full maturity and complete knowledge of what he himself was taught by him, so when he returns to get his church (or they died) they would be completely mature in Biblical truth and a perfect bride for Jesus:
2 Corinthians 11:2
”I am jealous for you with a godly jealousy. I promised you to one husband, to Christ, so that I might present you as a pure virgin (symbolic of a pure holy mature people) to him.”
But even Paul with all his warnings to them and even seeing how loyal these remaining Christians were to God, Jesus and their teachings he was afraid that somehow in some way Satan would eventually deceive even the loyal Christians into following a false warped ‘Christianity’ (a false perverted view of the Bible/what Jesus taught: even of Jesus himself) that would hinder them from serving and obeying Jesus:
2 Corinthians 11:3-4
“...I am afraid that just as Eve was deceived by the serpent’s cunning (referring to the event in Genesis 3:1-6) , your minds may somehow be led astray from your sincere and pure devotion to Christ…if someone comes to you and preaches a Jesus other than the Jesus we preached, or if you receive a different spirit from the [holy] Spirit you received, or a different gospel from the one you [originally] accepted,…”
Sadly, Both Paul and Peter prophesied that one day in the (not so distant) future, false teachers would either come to these remaining loyal Christians and make up different doctrines/stories to deceive them into following them/giving them their wealth:
2 Peter 2:2-3
“But [just as] there were also false prophets among the people [of ancient Israel], …there will [also] be false teachers among you. They will secretly introduce destructive heresies, even denying the sovereign Lord…In their greed these teachers will exploit you with fabricated stories. ”
or they simply would just not want to hear the believes that the original disciples taught them anymore: they would want to hear another false human-made doctrine to suit their own selfish desires:
2 Timothy 4:3-4
“...the time will come when people will not put up with sound (Biblically correct) doctrine. Instead, to suit their own desires, they will gather around them a great number of teachers to say what their itching ears want to hear.”
together this would cause many Christians to turn away from the original right path originally set up by the disciples and turn to a false belief(s) and thus cause massive division/confusion in the Church:
2 Peter 2:3
“...Many [Christians] will follow their depraved conduct and will bring the way of truth (the original Biblical/apostolic Christianity) into disrepute(bad reputation).”
2 Timothy 4:4
“...They will turn their ears away from the truth (the original apostolic Christianity) and turn aside to myths (false beliefs).”
Though they (and all other disciples) tried to warn the early churches they founded desperately about the dangers of following false teacher and their false believes they knew eventually in future generations of Christians that they would eventually end up rejecting their teaching for something made up by humans.
and sadly, that is exactly what happened!
Sources:
[1]
Jewish virtual library “The Tanakh” by American-Israeli Cooperative Enterprise
Website:
https://www.jewishvirtuallibrary.org/the-tanakh
[2]
Learn religions "What Is a Rabbi?
The Role of the Rabbi in the Jewish Community" by By Ariela Pelaia
Website:
https://www.learnreligions.com/what-is-a-rabbi-2076767
[3]
The New Testament (Specifically the Gospels: books of Matthew, Mark, Luke, and John)
[4]
[A] “The Nicolaitanes are the followers of that Nicolas who was one of the seven first ordained to the diaconate by the apostles. They lead lives of unrestrained indulgence. The character of these men is very plainly pointed out in the Apocalypse of John, [when they are represented] as teaching that it is a matter of indifference to practise adultery, and to eat things sacrificed to idols. Wherefore the Word (The Bible) has also spoken of them thus:
(Revelation 2:6)
‘But this thou hast, that thou hatest the deeds of the Nicolaitanes, which I also hate’”
From Verse 3-5 Chapter 26 “Doctrines of Cerinthus, the Ebionites, and Nicolaitanes.” Book 1 of “Irenaeus Against Heresies” (original Greek: Ἔλεγχος καὶ ἀνατροπὴ τῆς ψευδωνύμου γνώσεως”) by St. Irenaeus of Smyrna in 174 to 189 A.D.
from Christian Classics Ethereal Library : “Volume I. The Apostolic Fathers with Justin Martyr and Irenaeus”.
Website:
https://www.ccel.org/ccel/schaff/anf01.ix.ii.xxvii.html
[B] “...There was a Samaritan, Simon, a native of the village called Gitto, who in the reign of Claudius Caesar, and in your royal city of Rome, did mighty acts of magic, by virtue of the art of the devils operating in him. He was considered a god, and as a god was honoured by you with a statue, which statue was erected on the river Tiber, between the two bridges, and bore this inscription, in the language of Rome:--
"Simoni Deo Sancto," "To Simon the holy God."
And almost all the Samaritans, and a few even of other nations, worship him, and acknowledge him as the first god; and a woman, Helena, who went about with him at that time, and had formerly been a prostitute, they say is the first idea generated by him. And a man, Meander, also a Samaritan, of the town Capparetaea, a disciple of Simon, and inspired by devils, we know to have deceived many while he was in Antioch by his magical art. He persuaded those who adhered to him that they should never die, and even now there are some living who hold this opinion of his…All who take their opinions from these men, are,…called Christians…”
From CHAPTER XXVI -- MAGICIANS NOT TRUSTED BY CHRISTIANS. “The first apology” by St Justin (martyr) in 156 A.D. from Early Christian writings “Justin Martyr”
Website:
http://www.earlychristianwritings.com/text/justinmartyr-firstapology.html