The Church: from Greek, ekklesia, "the called out ones"
The Church is The One Bride of Christ
Ephesians 5 (NASB)
22Wives, be subject to your own husbands, as to the Lord.
23For the husband is the head of the wife, as Christ also is the head of the church, He Himself being the Savior of the body.
24But as the church is subject to Christ, so also the wives ought to be to their husbands in everything.
25Husbands, love your wives, just as Christ also loved the church and gave Himself up for her,
26so that He might sanctify her, having cleansed her by the washing of water with the word,
27that He might present to Himself the church in all her glory, having no spot or wrinkle or any such thing; but that she would be holy and blameless.
Christ is the head over his Church, of which is comprised those who have seen sancified ("set apart") to be his own as: one woman is set apart from all other women to be a man's one & only wife. Christ saves his church as he, himself, sanctifies and cleanses "her". He is preparing his church for the marriage that will happen when he returns. "She", his church, will be gloriously beautiful and without defect. "The perfect bride!" There is but One "Bride of Christ" whom he will totally have ready for himself when he returns.
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Christ's One and Only Church
Ephesians 1 (NASB)
3Blessed be the God and Father of our Lord Jesus Christ, who has blessed us with every spiritual blessing in the heavenly places in Christ,
4just as He chose us in Him before the foundation of the world, that we would be holy and blameless before Him In love
5He predestined us to adoption as sons through Jesus Christ to Himself, according to the kind intention of His will,
6to the praise of the glory of His grace, which He freely bestowed on us in the Beloved.
7In Him we have redemption through His blood, the forgiveness of our trespasses, according to the riches of His grace
8which He lavished on us. In all wisdom and insight
9He made known to us the mystery of His will, according to His kind intention which He purposed in Him.
God has no "secrets" regarding the one and only church; it's "mystery" has been fully revealed according the Father's will, purpose and plan, in all wisdom and insight. The grace and glory of God is completely realized in and through the One Church of the Lord Jesus Christ.
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The One Church Is: Those Who Believe: The Inheritors of Every Promise of God
Ephesians 1 (NASB)
13In Him, you also, after listening to the message of truth, the gospel of your salvation--having also believed, you were sealed in Him with the Holy Spirit of promise,
14who is given as a pledge of our inheritance, with a view to the redemption of God's own possession, to the praise of His glory.
15For this reason I too, having heard of the faith in the Lord Jesus which exists among you and your love for all the saints,
16do not cease giving thanks for you, while making mention of you in my prayers;
17that the God of our Lord Jesus Christ, the Father of glory, may give to you a spirit of wisdom and of revelation in the knowledge of Him.
18I pray that the eyes of your heart may be enlightened, so that you will know what is the hope of His calling, what are the riches of the glory of His inheritance in the saints,
19and what is the surpassing greatness of His power toward us who believe. These are in accordance with the working of the strength of His might
The church are those who, through faith, have 'heard the call of God to them' through the Gospel of Jesus Christ and have called back to Him (see Romans, chapter 10). They are promised the inheritance of God's one and only redemption. Till that redemption is fully realized at the second coming of Christ, the church grows in all wisdom and personal knowledge of God the Father.
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God Has Subjected All Things to Christ: Under and Through the Church
Ephesians 1 (NASB)
20which He brought about in Christ, when He raised Him from the dead and seated Him at His right hand in the heavenly places,
21far above all rule and authority and power and dominion, and every name that is named, not only in this age but also in the one to come.
22And He put all things in subjection under His feet, and gave Him as head over all things to the church,
23which is His body, the fullness of Him who fills all in all.
Christ is exalted over every rule, power, and authority. Through the church, which is the fullness of his body in the world, redemption and every divine purpose will be carried out. The church is both the recipent {benefactors}of God's salvation and the vehicle through which God's redemptive plan for humanity will be accomplished. The Divine Plan will be consummated when Christ returns.
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The One Church is Completely Immune From The Second Death
Revelation 2 (NASB)
8"And to the angel of the church in Smyrna write: The first and the last, who was dead, and has come to life, says this:
9'I know your tribulation and your poverty (but you are rich), and the blasphemy by those who say they are Jews and are not, but are a synagogue of Satan.
10'Do not fear what you are about to suffer. Behold, the devil is about to cast some of you into prison, so that you will be tested, and you will have tribulation for ten days Be faithful until death, and I will give you the crown of life.
11He who has an ear, let him hear what the Spirit says to the churches He who overcomes will not be hurt by the second death.'
Jesus promises all Christians, then and now, protection from those who blaspheme, though they may throw our bodies into prison and/or kill us [see Matt 10:28].
No one who "overcomes" by remaining faithful their calling to the Only Church of Jesus Christ will go to the Lake of Fire and experience the Second Death. It won't even "harm" them at all, says the Lord!
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There is and ever only will be:
One Church in One Body of "called out ones" over whom Jesus Christ is Lord, Savior, Head, and Groom. Christ will succeed in having the church, his Bride, totally ready for himself when he returns.
One Redemption, One Salvation, One Predestined Divine Plan of God the Father.
This plan is NO "mystery". There will be NO OTHER "secret postmortem church".
Saint Paul and John the Revelator were not gnostics and taught no "secrets".
The One Church of the Lord Jesus Christ is not gnostic.
The God of the Church is not a gnostic god.
Jesus Christ is not a gnostic savior.
I'm not a gnostic either!
Who knew?
I do!

Have a good day,
Rick