Isaiah48chapter 48

The furnace is a metalworker's furnace. Silver was refined by melting the ore with lead in a crucible so the impurities were drawn off and the bright metal left behind. God says he refined them, but not with silver — that is, not by the silver process and not for a profit — and chose them in the furnace of affliction. The exile is described as a smelting operation with a purpose.

The description of their stubbornness uses a farm animal. Your neck is an iron sinew and your brow is bronze — the ox that will not bend its neck for the yoke and drives its head against the goad. Anyone who had worked a stubborn animal knew the feeling exactly.

The reason God announced things in advance is stated bluntly, and it is not flattering. I declared them to you from the beginning; before it came to pass I showed you, so that you could not say, my idol has done them. He knew they would credit a statue, so he dated the prediction.

Then something new: from this time I make you hear new things, hidden things you have not known, created now and not long ago, so you cannot say, behold, I knew them. There is a difference between fulfilled prediction and fresh revelation, and the chapter marks it.

The command at the end is the departure order, and it comes with an instruction about how to leave: go out of Babylon, flee from the Chaldeans, with a voice of singing declare it, tell it out to the end of the earth, say, the LORD has redeemed his servant Jacob. And the guarantee is the wilderness precedent — they did not thirst when he led them through the deserts; he made water flow from the rock for them; he split the rock and the water gushed out.