Matthew 13:42

“And will cast them into the furnace of fire. There will be the weeping and gnashing of teeth.”

And all who have been in rebellion against God, and against the Son of Man, will be tossed into the furnace of fire to be burned up (compare Daniel 3:6 which this strongly echoes). The idea of the wicked ending up in fire is a constant one in Scripture, but it must not be applied literally (any more than must the pearly gates and pure gold of the new Jerusalem). It is rather a vivid picture depicting the awful end of the unbeliever in earthly terms. (Not that its non-literalness will make it any easier to bear, for it rather symbolises the awfulness of the antipathy of God (the wrath of God) against sin).

It probably arose initially from what men did with cities once they had captured them (Isaiah 1:7 and often). It continued with the idea of the burning rubbish dump outside Jerusalem on which ‘transgressors' would be cast (Isaiah 66:24), and the fact that fire was regularly the way of getting rid of what was useless (John 15:6) or offensive, and of punishing rebellious people, either as individuals (Daniel 3:6) or by burning their lands or their cities (Matthew 22:7). And it gradually developed into the idea of Gehenna, the place of the destruction of the wicked. It is symbolised in Revelation as a Lake of Fire (Revelation 20:14), where it is, however, the recipient of both spiritual beings (Satan), and political and religious systems (the wild beast and the false prophet), as well as of death and of the grave (Hades). It is the place where God disposes of all that spoils creation, the final Incinerator from which none who are not His can escape.

The weeping and gnashing of teeth is a regular picture of anguish and despair as men recognise what they have lost and forfeited (see also Matthew 13:50 ‘furnace of fire'; and compare Matthew 8:12, where their end is depicted as ‘outer darkness', that is, being excluded from the lights of the feast; Matthew 22:13 similarly ‘outer darkness'; Matthew 24:51 ‘a portion with the hypocrites'; Matthew 25:30 ‘outer darkness'). The emphasis in this phrase is on the value of what has been lost causing misery and despair.