In the OT, phrases like “weeping and gnashing of teeth”, “inextinguishable fire”, “worms that don't die”, “the fire of Gehenna”, are all used as metaphors for national destruction. (They're never used in the OT as metaphors for the eternal torment of individual immortal souls.)
A comment about evidence for Heaven and Hell in the Old Testament
I presume Allan is referring to Isaiah 66. But before I examine the claim that these phrases describing eternal torment are *only* metaphors for national destruction, a word about Hell and Heaven in the Old Testament. Regardless of the universalism debate, there isn't a great deal said in the Old Testament about life after death or eternity with God. In one way this is because the Old Testament is generally concerned with "life under the Sun" and the actions of God in this world. Admittedly the New Testament shows similarly narrow focus by concentrating mainly on the Christian experience and only occasionally taking a cosmic viewpoint, although more often the the Old Testament. This shouldn't be alarming, the word Trinity isn't mentioned in the Bible but the evidence for that way of understanding God still exists there in the text. So we have to carefully glean what we can from the Old Testament about what happens after death for both the wicked and the righteous.
For example: Daniel 12
There aren't many places where the Old Testament talks about the resurrection and interestingly in one of the few places it does, Daniel 12:1-3, eternal punishment is also mentioned. Again Daniel is a classic example of the prophetic style which describes both local and distant events, like a landscape depicting close valleys and distant vistas.
And many of those who sleep in the dust of the earth shall awake, some to everlasting life, and some to shame and everlasting contempt. (12:2)
A warning about presuppositions
Allan is uncomfortable with inerrancy and suggests we should be selective in our reading. I on the other-hand affirm inerrancy because God is coherent and loving. I also think given the sufficiency of Scripture, we should take a holistic approach to understanding the Bible. Both Allan and I present our cases based on respective presuppositions, so you need to evaluate our arguments but also evaluate our presuppositions.
This section of Isaiah is about the future, not just the future of Israel but the future of the Cosmos. You see this several times throughout Isaiah, a movement from prophecy about local events to prophecy about the distant future. Allan claimed that this section depicts "national destruction," the destruction of Israel. However the viewpoint is clearly cosmic not tightly Middle Eastern:
Thus says the Lord:
“Heaven is my throne,
and the earth is my footstool; (66:1)
Furthermore Isaiah only a few verses before had been describing the new heavens and the new earth.
The wolf and the lamb shall graze together; (65:25)
So with this distant future in mind Isaiah then contrasts the righteous;
he who is humble and contrite in spirit (66:2)
with the wicked;
These have chosen their own ways, (66:3)
God therefore plans some-sort of retributive punishment for them:
I also will choose harsh treatment for them (66:4)
It's only in verse 7 that Israel finally gets a mention. Here Isaiah sets the rewarded Israel in comparison to the upcoming judgement of the wicked. This isn't just the pathetic restoration at the end of the exile from Babylon but a glorious future restoration.
You shall see, and your heart shall rejoice;
your bones shall flourish like the grass; (66:14)
But God goes on to warn the cosmos:
gather all nations and tongues. (66:18)
and concludes the book of Isaiah with a description of how the wicked will be eternally tormented;
And they shall go out and look on the dead bodies of the men who have rebelled against me. For their worm shall not die, their fire shall not be quenched, and they shall be an abhorrence to all flesh.” (66:24)
Given the style of Isaiah and the context of this chapter, the introductory verses and the comparison of the wicked and the righteous right after Isaiah has described the new heavens and the new earth, it is right to draw the conclusion that Isaiah, nationality aside, is describing the eternal destruction of the wicked.