'Iron' in the Bible
And I, behold, I appoint thee this day as a strong city, and an iron pillar, and brazen walls, against the whole land; against the kings of Judah, against its princes, against its priests, and against the people of the land.
They are all the most rebellious of rebels, going about with slander: they are bronze and iron; they are all corrupters.
which I commanded your fathers in the day that I brought them forth out of the land of Egypt, from the iron furnace, saying, Hearken unto my voice and do them, according to all that I command you; so shall ye be my people, and I will be your God:
The sin of Judah is written with a style of iron, with the point of a diamond, engraven upon the tablet of their heart, and upon the horns of your altars;
Go and tell Hananiah, saying, Thus saith Jehovah: Thou hast broken the yokes of wood, and thou hast made in their place yokes of iron.
For thus saith Jehovah of hosts, the God of Israel: I have put a yoke of iron upon the neck of all these nations, that they may serve Nebuchadnezzar king of Babylon; and they shall serve him: and I have given him the beasts of the field also.