Their Worm Does Not Die

More often than not, the details that people associate with the Biblical hell are not included in the Bible itself, and in many cases even contradict what it does teach.  The most blatant of the cultural myths about the Christian hell is that it involves eternal conscious torment for every unsaved being.  The actual details the Bible does provide, such as how everyone would be punished according to their deeds (degrees of punishment because sins are not equally vile), the physicality of hell (Jesus speaks of people having their bodies in hell, so he is not describing a metaphysical space void of matter), and how cosmic death in hell is the ultimate penalty for sin instead of eternal torture [1], are not even generally recognized as the Biblical teachings on the matter.  

For all of the aforementioned details about hell that are included in the Bible, there is indeed much that is not elaborated upon.  Jesus does say that the physical body is punished in hell and not just the mind, but he does not specify what hell is supposed to look like or whether its physical environment is nothing but an actual lake of fire.  When multiple verses say that the wicked will be punished according to their deeds, they do not say if the general unsaved will be tormented for different durations of time at equal severities before their annihilation, or if they will be tormented prior to annihilation for an equal duration at different levels of pain.  However, these details are not necessary to understand the ideas that the Bible does posit about hell.  The same is true of Mark 9:47-48's description of the physicality of hell, as it states that is better to lose parts of one's body than to have a full body and be cast into hell, but casually mentions that "their worm does not die, and the fire is not quenched."

This reference to a worm is paralleled in Matthew 18, but this other part of the Bible does not reveal details about what exactly this worm is.  The mention of fire that goes unquenched refers to how the realm of hell itself is described as eternal (Matthew 18:8), made for Satan and his fellow fallen angels (Matthew 25:41), and this is entirely consistent with the many statements in the Bible about how unsaved humans, as opposed to the devil, are to be punished with an eternal death of consciousness (Ezekiel 18:4, Matthew 10:28, Romans 6:23, and so on).  That a realm will last forever does not mean everything inside of it must last forever.  Even so, Mark 9 specifically says that "their worm does not die" in hell without clarifying what precisely is being conveyed.  If literal, Jesus is saying that there is a worm/worms that devours the physical bodies of those in hell, living forever even after the unsaved perish.

Even though this does not bring much more to light, it is true that Mark 9 is paraphrasing Isaiah 66:22-24, where God is speaking of a new heavens and a new earth to which humanity will come, looking out at the corpses of God's enemies as their "worm," it is implied, consumes the dead flesh.  The onlookers likely experience hatred towards the wicked based upon the comment that the dead who rebelled against God are loathsome to "all mankind."  The seeming eschatological context of this is clear from its use of wording much like that of Revelation when it talks of a renewed physical creation.  The bodies are dead, which is consistent with the common Biblical teaching of annihilationism, and though 2 Peter 2:6 says that the unsaved will be burned to ashes instead of ceasing to exist as minds while leaving full bodies to exist forever, it is possible that even if Isaiah 66:22-24 is a literal description of the saved witnessing the aftermath of the wicked permanently dying on the level of consciousness, the bodies will persist for a while in the presence of a worm until they are reduced to ashes.

Regardless, the worm of Isaiah 66 (and Mark 9 by extension) is like terrestrial worms that feast on corpses, and it is clear from passages all throughout the Bible that general humanity is destined for death of the soul, without which the body is also dead.  Though Jesus does not give much clarity, it would seem that the Biblical hell is associated with some sort of worm.  This has not deterred some Christians from somehow thinking that the "worm" of Mark 9 is actually conscience as it torments the wicked, as if that in any way is present in the text of Mark 9 or the part of Isaiah 66 it paraphrases!  Of course, the kind of evangelical who would come to this non sequitur is likely the kind of Christian who genuinely thinks that the Bible is very literal in its teachings, yet he or she remains unaware of the fact that the literal words of the Bible do not teach that conscience is involved in the agony of hell or that all humans in hell exist forever, alive and in pain.  Whatever the worm of hell is, death of the spirit (the conscious mind) and the eventual deterioration of the body to ashes is what the Bible literally teaches is the ultimate, deserved fate of unrepentant humans.

[1].  https://thechristianrationalist.blogspot.com/2017/02/the-truth-of-annihilationism.html