Why would Paul have to say this to his followers concerning some saying the resurrection has already happened?
[which doesn't appear to occur until Revelation 20:5 "the first resurrection"?]
Strong's Concordance with Hebrew and Greek Lexicon
2Ti 2:18
who about the truth swerve<795>, saying the resurrection/ἀνάστασιν<386> already to have become/γεγονέναι<1096>
and they are subverting<396> the of-some<5100> faith.
become/γεγονέναι<1096>
Speech: Verb Parsing: Perfect Infinitive Active
18
οἵτινες περὶ τὴν ἀλήθειαν ἠστόχησαν, λέγοντες ἀνάστασιν ἤδη γεγονέναι,
καὶ ἀνατρέπουσιν τήν τινων πίστιν.
18
oitineV peri thn alhqeian hstochsan legonteV thn anastasin hdh gegonenai
kai anatrepousin thn tinwn pistin
Revelation 20 shows the Resurrection.
Revelation 20:5
The rest of the dead no they live until should be being finished<5055> the thousand years.
This the resurrection/ἀνάστασις <386>, the first.
20:5
οἱ λοιποὶ τῶν νεκρῶν οὐκ ἔζησαν ἄχρι τελεσθῇ1 τὰ χίλια2 ἔτη.
αὕτη ἡ ἀνάστασις ἡ πρώτη.
Scrivener 1894 Textus Receptus
oi de loipoi twn nekrwn ouk anezhsan ews telesqh ta cilia eth auth h anastasiV h prwth
Byzantine Majority
kai oi loipoi twn nekrwn ouk ezhsan acri telesqh ta cilia eth auth h anastasiV h prwth.
.
No need to go into the Greek to 'Proof Text" what is exegetically clear as crystal.
As to answer your question below -
Why would Paul have to say this to his followers concerning some saying the resurrection has already happened?
We need to read 2 Timothy 4 to get a better understanding of why it concerned Paul. The resurrection that was being advocated by the Greeks Hymenaeus and Philetus was a spiritual one and not a bodily one and this was undermining the faith because faith requires self-sacrifice of what is hoped for and yet not seen. Since self-preservation would be the mindset of the day if it were merely a spiritual resurrection, then the commission to preach from the Gospel would have self-preservation as the underlying extrinsic motivator and not self-sacrifice as the intrinsic motivator that promises something that cannot be seen nor attained in this temporal life.
"of Christ Jesus, who will judge the living and the dead, in view of his appearing and his kingdom"
Paul is pointing to the biologically dead in Christ.
"Preach the word; be prepared in season and out of season"
Paul is encouraging the Church not to be complacent. A self-preservation mindset serves to feed complacency, especially when a choice is there as to whether one chooses to stick their head out on the chopping block for Christ for the sake of his Gospel or to live another day.
"For the time will come when people will not put up with sound 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."
The itchy ear is a concept of feeding people what they want to hear and not necessarily what the truth entails. Hymenaeus and Philetus who were Greeks seem to be those Greek philosophic teachers who taught that the resurrection is past and that it was a spiritual one, much like how Preterists teach for their 70AD narrative.
The background to what Greeks believed before they were converted to Christianity within their philosophical circles is that physical matter, in general, is inherently evil and that goodness is not material but spiritual within the ethereal realm of the pagan gods they once worshipped. So the theological networkings of the Greeks Hymenaeus and Philetus is a Preterist variation of the resurrection that does not emphasise a bodily resuscitation, whereby the Greek philosophers of their days considered inherently evil.
They will turn their ears away from the truth and turn aside to myths. But you, keep your head in all situations, endure hardship, do the work of an evangelist, discharge all the duties of your ministry.
Hymenaeus and Philetus were turning away people to Greek Myths.
So what was stopping the adherents of the Greeks Hymenaeus and Philetus was that itchy ears were the mindset of the day for the feel-good experience, rather than self-sacrifice ethos, by enduring hardship (tribulation) and by discharging all the duties of a Christian's ministry. The Hymenaeus and Philetus camp were being accused by Paul for not discharging
ALL the duties of their ministry because there was no intrinsic motivation to stick their necks out on the chopping block.
For I am already being poured out like a drink offering, and the time for my departure is near. I have fought the good fight, I have finished the race, I have kept the faith.
Paul now compares his self-sacrifice as a Testator of Hebrews 9:16-17 and Hebrews 12:4, who has resisted to the point of shedding his blood for the faith in Christ Jesus and by so doing has discharged fully his obligations as a minister of Christ.
There is no resurrection for a Testator for Christ until there must also of necessity be the biological death of the testator, as biological death is the demarcation line that now places the Testator as a recipient of the judgement of the works of faith done in the earthly body, in order to receive their eternal inheritance (Hebrews 9:15). Paul in 2 Timothy 4:1 & 8 would say -
"of Christ Jesus, who will judge the living and
the biologically dead"
"Now
there is in store for me the crown of righteousness, which the Lord, the righteous Judge, will award to me on that day—and not only to me, but also to all who have longed for his appearing."
The sequence for the Lord's appearance is self-sacrifice in preaching the Gospel, biological death, judgement before the righteous Judge, then resurrection in whatever form that is the glorified form, whereby the witness will then claim their eternal inheritance and to receive their Crown of Life.
No witness is raised or receives their Crown of Life until they keep the faith even onto biological death as Jesus said in Revelation 2:10.
What the Greeks Hymenaeus and Philetus of the past, along with the Preterists of today are preaching is the itchy ears gospel that is absent of self-sacrifice and one that is a feel-good camp who claim to already have been judged righteous by the righteous Judge within this temporal life, before they have even shed their blood (biologically died).
The Greeks Hymenaeus and Philetus were teaching a resurrection that was spiritual and one that the recipients get to enjoy the blessings without having to make further sacrifices because Christ has made the sacrifice for them and this is the same theology that the Preterists use in opposition to every exegetic argument to the contrary -
it is appointed unto men once to die, but after this the judgment: So Christ was once offered to bear the sins of many; and unto them that look for him shall he appear the second time without sin unto salvation.
The witnesses in Christ must die biologically before they are judged righteous by the righteous judge in order to receive their crown of life and not before. The Preterists 70AD resurrection narrative and Hymenaeus and Philetus resurrection narrative are birds of the same feather and in this respect are false teachings for the itchy ears gospel. The emphasis of beholding the Lord's Appearing on that Day is when the Testator is presented before the risen glorified Lord as one of the Holy Ones that accompany him, within their sinless post mortem bodily resuscitated form, whatever that may be.
John eloquently worded it this way -
1 john 3:2
Dear friends, now we are children of God, and what we will be has not yet been made known. But we know that when Christ appears, we shall be like him, for we shall see him as he is.