What is the Biblical basis for annihilationism or the conditionalist doctrine of hell?

Credit to user Mark Edward from whom this text is taken, from the end of a long answer to a different question

I’m pasting it because it is the only text we found on the se addressing what Annihilationists use as basis. If you dislike it, you can try to provide a better answer:

Annihilationism

Where conditionalism defines human immortality as conditional upon a right relationship with God, annihilationism is defined as a direct punishment of death from God. Qualitatively, there is no distinction between 'death' and 'annihilation'; the latter word is used solely to clarify just what it is that 'death' consists of.

Again, on a broader level, annihilationists believe the bible teaches that humans who are ultimately unrepentant will suffer death / cessation of existence. Poetic idioms in the Psalms are said to accurately describe a lack of existence, prophetic metaphors are said to capture the essence of a lack of existence, and the 'plain meaning' of basic words are said to describe a lack of existence directly.

The final fate of the unsaved is:

• To vanish like smoke (Psalm 37:20)
• Like the snail that melts into slime, like the stillborn child that never sees the sun (Psalm 58:8)
• Like smoke that is driven away, like wax melts before a fire (Psalm 68:2)
• Like a dream when one awakes (Psalm 73:20)
• Destroyed, wiped out all remembrance of them (Isaiah 26:14)
• Stubble in a burning oven; leaving them neither root nor branch; ashes under the soles of the righteous' feet (Malachi 4:1-3)
• Slaying of body and soul (Matthew 10:28)
• Eternal punishment (Matthew 25:46)
• Death (Romans 6:23)
• Eternal destruction (2 Thessalonians 1:9)
• Like Sodom and Gomorrah: turned to ashes, and condemned to extinction (2 Peter 2:6)
• The second death (Revelation 2:11ff)

This is going to be an incomplete answer because this question is broad and is connected to other doctrines like the nature of man, the state of the dead and the judgment.

Since the beginning of sin there was only two possibilities for mankind: life as offered by Christ or death. It was not eternal life in heaven or eternal life in hell.

Genesis 2:17 But of the tree of the knowledge of good and evil, thou shalt not eat of it: for in the day that thou eatest thereof thou shalt surely die.

Romans 6:23 For the wages of sin is death; but the gift of God is eternal life through Jesus Christ our Lord.

John 3:16 For God so loved the world, that he gave his only begotten Son, that whosoever believeth in him should not perish, but have everlasting life.

These verses above are referring to the second death and not the first death.

John 8:51 Verily, verily, I say unto you, If a man keep my saying, he shall never see death.

The second death is complete destruction of the wicked in the lake of fire as described in the verses below.

Psalm 37:20 But the wicked shall perish, and the enemies of the Lord shall be as the fat of lambs: they shall consume; into smoke shall they consume away.

Matthew 10:28 And fear not them which kill the body, but are not able to kill the soul: but rather fear him which is able to destroy both soul and body in hell (γέεννα).

2 Thessalonians 1:8,9 In flaming fire taking vengeance on them that know not God, and that obey not the gospel of our Lord Jesus Christ: Who shall be punished with everlasting destruction from the presence of the Lord, and from the glory of his power;

Malachi 4:1,3 For, behold, the day cometh, that shall burn as an oven; and all the proud, yea, and all that do wickedly, shall be stubble: and the day that cometh shall burn them up, saith the Lord of hosts, that it shall leave them neither root nor branch. And ye shall tread down the wicked; for they shall be ashes under the soles of your feet in the day that I shall do this, saith the Lord of hosts.

Sodom and Gomorrha are set forth as examples of suffering eternal fire in Jude, but they were clearly destroyed.

Jude 1:7 Even as Sodom and Gomorrha, and the cities about them in like manner, giving themselves over to fornication, and going after strange flesh, are set forth for an example, suffering the vengeance of eternal fire.

2 Peter 2:5,6 And spared not the old world, but saved Noah the eighth person, a preacher of righteousness, bringing in the flood upon the world of the ungodly; And turning the cities of Sodom and Gomorrha into ashes condemned them with an overthrow, making them an ensample unto those that after should live ungodly;

We are judged by our works so this means that everyone will have different rewards not the same reward. Revelations 20:13,14 And the sea gave up the dead which were in it; and death and hell delivered up the dead which were in them: and they were judged every man according to their works. And death and hell were cast into the lake of fire. This is the second death.

The word forever and eternal (olam in the old testament and aionios in the new testament) in the bible does not necessarily mean an endless length of time it can also mean an age. Take for example Jonah 2:6 and 1 Samuel 1:22. In both these cases forever is clearly referring to a specific amount of time 3 days and nights in Jonah and to the end of Samuel’s life in Samuel. It really depends on the context of the verse itself. In many cases can just when dealing with the punishment of the wicked it could mean an ambiguous time until all the wicked are burned up or it could be referring to the nature of the punishment which has eternal consequences (eternal separation from God in death).

Death is not the same as being annihilated.

There are two ways of defining dead.

1. the lack of physical life - not breathing, no consciousness, no pulse and eventually, no body. Just 'dust' remains and maybe some teeth! From this death, life is again possible by a resurrection at the time of God's choosing.
2. Spiritually dead is the state of being dead to sin, even if you are still breathing. Like the term, 'dead man walking' - referring to a prisoner who is sentenced to death, and is on his way to dying - he is essentially dead already! The spiritually dead includes all men who ever lived, except Jesus. All are essentially waiting for the execution of the penalty handed to Adam - "the penalty of sin is death". So even while they live, they are dead. These too can be raised to new life - physical or spiritual, by God.

Annihilation is the removal (or expiry) of the resurrection option. They simply no longer exist in any form. This can only happen after the second death mentioned in Rev 20. This is not 'dead' in either of the previously noted states - it is irreversible.

The biblical basis for this understanding is not based on what scripture explicitly says this, but what it does not say.

The dead will not live, the departed spirits will not rise; Therefore You have punished and destroyed them, And You have eliminated all remembrance of them. Is 26:14

The context of this passage is not end-time, post second-death; it is a song about life and troubles and the God who provides.

What we do have is no mention of any evil person being given eternal life. None! How can the wicked be tormented forever in some kind of demented, spiteful God scenario who takes delight in giving life to all and letting the wicked suffer for eternity!

As explained here, eternity does not have mean 'forever' and punishment does not mean torture or even death.

In the absence of scripture and the biased 'hellfire' interpretations like Matt 25:46, it seems many would rather make up what they want and pursue a theology not of the bible, but of men, desperate to justify their jobs, influence and income.

Certainly the theology of an eternal hellfire for the wicked is intended to extinguish the true revelation of the Judgement and the true God who is Saviour first and Destroyer second. Also addressed in the link provided.

After the 'second death' Rev 20:14, the next revelation in Rev 21 is,

Then I saw a new heaven and a new earth; for the first heaven and the first earth passed away, and there is no longer any sea...

This is a time when all physical life is gone. All remaining have spirit lives and life eternal.

God Himself will be among them, 4 and He will wipe away every tear from their eyes; and there will no longer be any death; there will no longer be any mourning, or crying, or pain; the first things have passed away.” v3

At this point, God's plan of salvation has been completed - all created humanity that has accepted Christ as their Saviour has been changed to spirit life.

What we are also told is that 'God is love' - torturing a broken and deceived humanity is not part of His plan. He will however hold to account the perpetrator of evil in ways that we are not privy to.