Jesus establishes the Church:
Matthew 16:[15] Jesus saith to them: But whom do you say that I am?
[16] Simon Peter answered and said: Thou art Christ, the Son of the living God. [17] And Jesus answering, said to him: Blessed art thou, Simon Bar-Jona: because flesh and blood hath not revealed it to thee, but my Father who is in heaven. [18] And I say to thee: That thou art Peter; and upon this rock I will build my church, and the gates of hell shall not prevail against it. [19] And I will give to thee the keys of the kingdom of heaven. And whatsoever thou shalt bind upon earth, it shall be bound also in heaven: and whatsoever thou shalt loose upon earth, it shall be loosed also in heaven. [Matthew 16:19] [Latin] [20] Then he commanded his disciples, that they should tell no one that he was Jesus the Christ.
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There are well over 33,000 sects “scattered” outside the one Church founded by Christ.
“And he took the cup and said, Drink of this, all of you. This cup is the NEW Covenent in My blood.”
The Ekklesia of God is that locality where His Word (Logos), is rightly preached and where His Sacraments are ritely practiced. The Feast of Pentecost celebrates the Ekklesia of the post-resurrection (new berith) where-in sins are immediately forgiven through the Sacraments and the preaching of the Gospel.
There has always been a Christian ekklesia wherever there has been God’s forgiveness of Sins through Christ (pre- and post- incarnate.) The Old Testament shows God forgiving even the sins of Adam and Eve through Christ (Gen 3:15). Fast forward to many examples, not limited to: The Snake on the pole (christ typology), the parting of the Red Sea (baptism) and David’s repentance (direct forgiveness).
The marks of the Church, Gospel preaching and Sacraments reverently administered, have existed from time memorial. The change we have for the last 2000+ years is simply because God inserted Himself, bodily, into time to be that thing we could not - perfect.