What is the furnace of fire in Matthew 13:42?

“Whatever ‘the furnace of fire’ may mean here … this at all events is certain, that they point to some doom so intolerable that the Son of God came down from heaven and tasted all the bitterness of death that he might deliver us from ever knowing the secrets of anguish, which … are shut up in these terrible words, ‘there shall be wailing and gnashing of teeth’ (22:13).”

Trench quoted by R. C. H. Lenski in Interpration of St. Matthew’s Gospel