Hebrews is written to a people that are only partakers if they hold the beginning of their confidence steadfast to the end
Hebrews 3:14 For we are made partakers of Christ, if we hold the beginning of our confidence stedfast unto the end;
As their salvation is relying on their faith to get them saved
1 Peter 1:7 That the trial of your faith, being much more precious than of gold that perisheth, though it be tried with fire, might be found unto praise and honour and glory at the appearing of Jesus Christ:
1 Peter 1:8 Whom having not seen, ye love; in whom, though now ye see him not, yet believing, ye rejoice with joy unspeakable and full of glory:
1 Peter 1:9 Receiving the end of your faith, even the salvation of your souls.
1 Peter 1:10 Of which salvation the prophets have enquired and searched diligently, who prophesied of the grace that should come unto you:
1 Peter 1:11 Searching what, or what manner of time the Spirit of Christ which was in them did signify, when it testified beforehand the sufferings of Christ, and the glory that should follow.
1 Peter 1:12 Unto whom it was revealed, that not unto themselves, but unto us they did minister the things, which are now reported unto you by them that have preached the gospel unto you with the Holy Ghost sent down from heaven; which things the angels desire to look into.
1 Peter 1:13 Wherefore gird up the loins of your mind, be sober, and hope to the end for the grace that is to be brought unto you at the revelation of Jesus Christ;
While people living today in the dispensation of the grace of God are partakers by the gospel
Ephesians 3:6 That the Gentiles should be fellowheirs, and of the same body, and partakers of his promise in Christ by the gospel:
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As our salvation relies solely on the Lord's faith 2000 years ago in our place!
Romans 3:21 But now the righteousness of God without the law is manifested, being witnessed by the law and the prophets;
Romans 3:22 Even the righteousness of God which is by faith of Jesus Christ unto all and upon all them that believe: for there is no difference:
Romans 3:23 For all have sinned, and come short of the glory of God;
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1 Corinthians 15:1 Moreover, brethren, I declare unto you the gospel which I preached unto you, which also ye have received, and wherein ye stand;
1 Corinthians 15:2 By which also ye are saved, if ye keep in memory what I preached unto you, unless ye have believed in vain.
1 Corinthians 15:3 For I delivered unto you first of all that which I also received, how that Christ died for our sins according to the scriptures;
1 Corinthians 15:4 And that he was buried, and that he rose again the third day according to the scriptures:
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Galatians 1:3 Grace be to you and peace from God the Father, and from our Lord Jesus Christ,
Galatians 1:4 Who gave himself for our sins, that he might deliver us from this present evil world, according to the will of God and our Father:
Galatians 1:5 To whom be glory for ever and ever. Amen.
To say that anyone need to do something to be saved or stay saved is a denial of the gospel of our salvation. It is in opposition to the truth of the gospel.
That's a lot of reading ability. You're reading your meaning into everything you quoted. When you do so you're also directly contradicting a mass of scripture and a lot of Paul's writings as well. Why all the effort to make Paul argue with himself? He doesn't. The only way to make Paul argue with himself is to read a position into his statements rather than using the entirety of his writings to understand his position.