fur'-nas: The word is used in the Old Testament English Versions of the Bible to translate several Hebrew words:
Kibhshan, in Ge 19:28, where the smoke of the destruction of the cities of the plain is said to have ascended "as the smoke of a furnace"; in Ex 9:8, where Yahweh commands to take "handfuls of ashes of the furnace and .... sprinkle it toward heaven," etc.
Kur, in De 4:20, where Yahweh is represented, when speaking of taking the children of Israel out of Egypt, as taking them "out of the iron furnace."
`Alil in Ps 12:6, where "the words of Yahweh" are said to be "pure," "as silver tried in a furnace"; compare Pr 17:3, "furnace for gold."
`Attun, in Da 3:6, where mention is made of "a burning fiery furnace" into which Daniel and his companions were cast. There is good reason to believe that these words all stand for either a brick-kiln or a smelting furnace.
In the New Testament a notable figurative use is made of the word in the phrase "the furnace of fire," he kaminos tou puros. It is found in the parable of the Tares (Mt 13:42) as part of the remarkable imagery of that parable; while in the companion parable of the Drag-Net (Mt 13:50) it stands as a symbol of the final destiny of the impenitent, a synonym of "hell"; compare Jer 29:22; Da 3:6,22; Re 20:14-15, etc., and "eternal fire" (Mt 25:41), "unquenchable fire" (Mt 3:12), "the Gehenna of fire" (Mt 5:22 margin; Mt 18:9 parallel Mr 9:43 margin, etc.). A fact which modern travelers speak of, that furnaces for punishment have been found in Persia as elsewhere in the East, sheds some light upon this use of the expression "the furnace of fire."
George B. Eager