Question: "What is the worm that will not die in Mark 9:48?"
Answer: Jerusalem’s ancient garbage dump—a place called Gehenna—was illustrative of the ceaseless agonies of hell. This dump was on the south side of Jerusalem. In Old Testament times, children had been sacrificed to idols there (2 Kings 23:10); in Jesus’ day, it was a place burning with constant fires to consume the waste that was thrown there. The material burned there included everything from household trash to animal carcasses to convicted criminals (Jeremiah 7:31–33). Needless to say, the Jews considered Gehenna a cursed place of impurity and uncleanness.
The word translated “hell” in Mark 9:43 is the Greek word Gehenna, which comes from the Hebrew name for a place called the “Valley of Hinnom.” Jesus uses this place to paint a vivid image of what hell is like. The Jewish people often associated the Valley of Hinnom with spiritual death.
In Mark 9:48, when Jesus says, “Where their worm does not die and the fire is not quenched” (ESV), He is quoting from Isaiah 66:24: “They will go out and look on the dead bodies of those who rebelled against me; the worms that eat them will not die, the fire that burns them will not be quenched, and they will be loathsome to all mankind.” In both texts the word translated as “worm” literally means “grub” or “maggot.” A maggot would have an obvious association with a dump like Gehenna where dead bodies are thrown; however, the maggot Christ speaks of “will not die.”
Taken at face value, this text is one of the most horrific descriptions of what hell is like. The thought of eternal torment, likened to maggots eating away at a rotting corpse, is undoubtedly ghastly. Hell is so awful that Christ said, figuratively speaking, it’s better to cut off the hand that causes you to sin than to end up in hell (Matthew 5:30).
Mark 9:48 does not mean that there are literal worms in hell or that there are worms that live forever; rather, Jesus is teaching the fact of unending suffering in hell—the “worm” never stops causing torment. Notice that the worm is personal. Both Isaiah 66:24 and Mark 9:48 use the word their to identify the worm’s owner. The sources of torment are attached each to its own host.
Some Bible scholars believe the “worm” refers to a man’s conscience. Those in hell, being completely cut off from God, exist with a nagging, guilty conscience that, like a persistent worm, gnaws away at its victim with a remorse that can never be mitigated. No matter what the word worm refers to, the most important thing to be gained from these words of Christ is that we should do everything in our power to escape the horrors of hell, and there is only one thing to that end—receiving Jesus as the Lord of our lives (John 3:16).