'Iron' in the Bible
For, behold, I have made thee this day a defenced city, and an iron pillar, and brasen walls against the whole land, against the kings of Judah, against the princes thereof, against the priests thereof, and against the people of the land.
They are all grievous revolters, walking with slanders: they are brass 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, Obey my voice, and do them, according to all which I command you: so shall ye be my people, and I will be your God:
The sin of Judah is written with a pen of iron, and with the point of a diamond: it is graven upon the table of their heart, and upon the horns of your altars;
Go and tell Hananiah, saying, Thus saith the LORD; Thou hast broken the yokes of wood; but thou shalt make for them yokes of iron.
For thus saith the LORD 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.