Matthew 8:12 says, “But the children of the kingdom shall be cast out into outer darkness: there shall be WEEPING AND GNASHING OF TEETH.” We also have this expression in Matthew 13:42, 13:50, 22:13, 24:51, 25:30, and Luke 13:28. As you mentioned, these verses come out of the ‘Synoptic’ Gospels which are Matthew, Mark, and Luke. In speaking of this place where there is weeping and gnashing of teeth, ‘outer darkness’ is also mentioned in Matthew 8:12, 22:13, and 25:30. These are the only three verses where this phrase is used. So in this gloomy darkness, those cast into it will continually weep in utter despair and hopelessness, and will gnash (grind) their teeth in violent anger towards God. Whether referring to this place as he taught of the judgment of God, or speaking in parables about this place, it is always synonymous with the place of eternal judgment…Hell.

We find another term describing this place of eternal suffering. Mark 9:44 speaks of that place, “Where their worm dieth not, and the fire is not quenched. This phrase is also used by Mark in verses 46 and 48. The worms never dies because there is a vast quantity of bodies that are being consumed, yet can never be consumed as those there will suffer for eternity. The expression comes from Isaiah 66:24, “And they shall go forth, and look upon the carcases of the men that have transgressed against me: for THEIR WORM SHALL NOT DIE, NEITHER SHALL THEIR FIRE BE QUENCHED; and they shall be an abhorring unto all flesh.”

Where is this place? That is hard to tell. Scripture often speaks of Hell as ‘down’. 2 Peter 2:4, “For if God spared not the angels that sinned, but CAST THEM DOWN TO HELL, and delivered them into chains of darkness, to be reserved unto judgment.” Psalms 55:15 says, “Let death seize upon them, and LET THEM GO DOWN QUICK INTO HELL: for wickedness is in their dwellings, and among them.” With these, and other verses, we get the impression of Hell being in the center of the earth. Of course, if we could dig down into the center of the earth, we would not find Hell. Even as Heaven is described as being ‘up’, we could not fly high enough to find it. These are spiritual dwellings and cannot be located with carnal devises. We might think of it like this, “Hell IS where God IS NOT.” Hell will be composed of those who rejected the Lord Jesus Christ as their Lord and Savior. It is a place of “weeping and gnashing of teeth”, a place of “outer darkness”. It is a place “where the worm dieth not.” It is a “lake of fire” (Revelation 20:10), a place of “everlasting punishment.” (Matthew 25:46) Hell does not bring annihilation but rather it is the place of eternal separation from God. How terrible that place is!

Where Hell causes “weeping and gnashing of teeth”, being in the presence of the Lord brings “fullness of joy.” (Psalm 16:11) “Choose you this day.” (Joshua 24:15) (260.10)