What is the worm that will not die mentioned in Mark 9:48?

TL;DR:

The “worm that does not die” in Mark 9:48 is a way of figuratively depicting the everlasting torment of hell. The horrifying and everlasting nature of hell should encourage believers to share the good news of how Christ saved us from it.

what does the bible say?

In Mark 9:48 Jesus, quoting from Isaiah 66:24, describes hell as "where their worm does not die and the fire is not quenched." This verse is found within a larger portrayal of the horrors of hell, using a place called Gehenna—the garbage dump of ancient Jerusalem—as an illustration. The Greek word Gehenna, translated as "hell" in Mark 9:43, originates in the Hebrew name for a place known as the "Valley of Hinnom." It was located on the south end of Jerusalem and had been a site for pagan child sacrifices during Old Testament times (2 Kings 23:10). During Jesus' lifetime, Gehenna had a constant fire burning to dispose of the waste left there—from regular household trash to the carcasses of animals and convicted criminals (Jeremiah 7:31–33). Because of all this, the Jews considered Gehenna to be a cursed place full of filth. It was an apt representation of hell, a place so horrific that Christ said it would be better to cut off a hand or foot or put out an eye if those cause us to sin. Being maimed is preferable than ending up in hell (Mark 9:43–47). The Bible passages about hell show the urgency of receiving Christ as Savior, making Him Lord of our lives, and sharing the good news of Him with others (John 3:16).

from the old testament

Second Kings 23 relates King Josiah’s attempts to restore Judah to proper worship. As part of that, Josiah “defiled Topheth, which is in the Valley of the Son of Hinnom, that no one might burn his son or his daughter as an offering to Molech” (2 Kings 23:10). The Valley of Hinnom was a place where pagans and some wicked kings of Israel sacrificed their children to fire (2 Chronicles 28:3). It was later used as a garbage dump in ancient Jerusalem, where a fire was kept burning to destroy the refuse left there. This place is referred to as Gehenna in the Greek scriptures, which is the word used for hell in Mark 9:48.
This place of torment is mentioned in Isaiah 66:24, the passage Jesus quotes in Mark 9:48: “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.” The judgment of God against His enemies is depicted as never-ending torment.
The Valley of Hinnom is mentioned by Jeremiah in his prophecy of the Babylonian conquest of Judah: “They built the high places of Baal in the Valley of the Son of Hinnom, to offer up their sons and daughters to Molech, though I did not command them, nor did it enter into my mind, that they should do this abomination, to cause Judah to sin” (Jeremiah 32:35). The evil that went on in the Valley was an “abomination” to God. The Valley of Hinnom would become an apt symbol of hell.

from the new testament

In Mark 9:48 Jesus quotes Isaiah 66:24 in describing hell as “where their worm does not die and the fire is not quenched.” In both verses, the word for "worm" refers to a "maggot" or "grub." Maggots are associated with death and decay. What's different about the maggot Christ mentions is that it "will not die." The verse emphasizes the everlasting nature of the fire and the worm. Just before this verse, Christ says it would be better to cut off a hand or foot and to put out an eye if they cause us to sin (Mark 9:43–47). The eternal consequences of sin are so horrific that maiming would be preferable to hell.
Second Thessalonians 1:9 describes the fate of those who oppose God: “They will suffer the punishment of eternal destruction, away from the presence of the Lord and from the glory of his might.” Those who are in hell will suffer torment because they will be separated forever from the goodness and glory of the Lord. The torments described in Mark 9:48 are figurative representations of the ultimate torment of being permanently alienated from God.
Revelation 20:10 depicts the horrors of hell as a just punishment for enemies of God: “and the devil who had deceived them was thrown into the lake of fire and sulfur where the beast and the false prophet were, and they will be tormented day and night forever and ever.” The existence of hell is a just sentence for those who reject God and lie about Him (as Satan and false prophets do). Those who reject God end up away from Him forever

implications for today

People don’t like to think about hell. In fact, some try to explain away its existence as a myth, or they claim a loving God wouldn’t allow such a place to exist. But the Bible attests to hell being real. Hell is real because a just God cannot tolerate sin. He sent His Son to pay for our sins to rescue us from hell. People either choose an eternity with Christ or choose an eternity in hell. The horrors of hell are so egregious that Christians should be motivated to do our part to tell others about how Christ saved us from such eternal torment. In fact, Jesus tasked believers with doing so (Matthew 28:18–20; Romans 10:14–15). Showing agape love toward our neighbors means telling them about Christ (John 13:34–35). We are responsible for sharing the gospel, and God is responsible for saving. We shouldn’t selfishly bury the gift of the good news that God has blessed us with. Our loving Father gave us a way to salvation through His Son. We must share that with others. Those who reject His free gift of eternal salvation end up where they have chosen. The Bible passages about hell show the urgency of receiving Christ as Savior, making Him Lord of our lives, and sharing the good news of Him with others (John 3:16).

understand

The "worm that does not die" in Mark 9:48 symbolizes everlasting torment in hell.
The “worm that will not die” is associated with Gehenna, a literal site in Jerusalem known for its perpetual fires and decay.
The reality of hell emphasizes the importance of evangelism, motivating believers to share the gospel and warn others about the eternal consequences of rejecting Christ.

reflect

How does the imagery of the "worm that does not die" shape your understanding of sin and its consequences?
Considering the description of hell in Mark 9:48, how does this inspire you to share the gospel with others?
How do you reconcile the existence of hell with the belief in a loving God? How does this impact your view of Christ's sacrifice?

engage

How did the historical understanding of Gehenna influence Jewish views on hell during Jesus' time?
What common themes about judgment and separation from God can you identify by comparing Mark 9:48 with Revelation 20:10 and 2 Thessalonians 1:9?
What does the concept of hell reveal about God's justice and holiness? How does this relate to our understanding of grace and salvation?