Often portable, Ge 15:17. They were used for melting the precious metals, Pr 17:3. The furnace into which Daniel's three friends were cast was large, and remained open after they were cast in, Da 3. The fearful punishment spoken of in Jer 29:22 is still used in the East. The word furnace is used to illustrate a state of oppression, De 4:20, and of affliction, Isa 48:10.
When the sun had set and it was dark, a smoking fire pot and a flaming torch appeared and passed between the divided [animals].
But the Lord selected you and brought you out of Egypt's iron furnace to be a people for His inheritance, as you are today.
A crucible is for silver and a smelter for gold, but the Lord is a tester of hearts.
Look, I have refined you, but not as silver; I have tested you in the furnace of affliction.
Holman Christian Standard Bible®, Copyright © 1999, 2000, 2002, 2003, 2009 by Holman Bible Publishers.