Your sky that is over your head shall be brass, and the earth that is under you shall be iron.
Because I knew that you are obstinate, and your neck is an iron sinew, and your brow brass;
Your bars shall be iron and brass. As your days, so your strength will be.
For, behold, I have made you this day a fortified city, and an iron pillar, and bronze walls, against the whole land, against the kings of Judah, against its princes, against its priests, and against the people of the land.
Arise and thresh, daughter of Zion; for I will make your horn iron, and I will make your hoofs brass; and you will beat in pieces many peoples: and I will devote their gain to Yahweh, and their substance to the Lord of the whole earth.
They had breastplates, like breastplates of iron. The sound of their wings was like the sound of chariots, or of many horses rushing to war.
The fourth kingdom shall be strong as iron, because iron breaks in pieces and subdues all things; and as iron that crushes all these, shall it break in pieces and crush.
Whereas you saw the feet and toes, part of potters' clay, and part of iron, it shall be a divided kingdom; but there shall be in it of the strength of the iron, because you saw the iron mixed with miry clay.
Iron sharpens iron; so a man sharpens his friend's countenance.