And your heaven that is over your head shall be bronze, 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 bronze;
Your shoes shall be iron and bronze; and as your days, so shall your strength be.
For, behold, I have made you this day a fenced 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, O daughter of Zion: for I will make your horn iron, and I will make your hoofs bronze: and you shall beat in pieces many people: and I will consecrate their gain unto the LORD, and their wealth unto the Lord of the whole earth.
And they had breastplates, as it were breastplates of iron; and the sound of their wings was as the sound of chariots of many horses running to battle.
And the fourth kingdom shall be strong as iron: since iron breaks in pieces and subdues all things: and as iron that breaks all these, shall it break in pieces and bruise.
And as you saw the feet and toes, part of potter's clay, and part of iron, the kingdom shall be divided; but there shall be in it the strength of the iron, just as you saw the iron mixed with miry clay.
Iron sharpens iron; so a man sharpens the countenance of his friend.