Charles Ellicott Commentary Matthew 13:42

"and shall cast them into the furnace of fire: there shall be the weeping and the gnashing of teeth." — Matthew 13:42 (ASV)

Into a furnace of fire—better, the furnace—that is, the furnace of Gehenna, in which there will be “the wailing and gnashing of teeth” (see the notes on Matthew 8:12).