And thy heavens which are over thy head shall be brass, and the earth that is under thee shall be iron.
Because I know that thou art obstinate, and thy neck is an iron sinew, and thy brow bronze;
Thy locks shall be iron and brass; and as thy days, so shall thy strength be.
For, behold, I have made thee this day as a defenced city and as an iron pillar and as a wall of brass upon all the earth 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 thine horn iron, and I will make thy hoofs bronze; and thou shalt break in pieces many peoples; and thou shalt consecrate their spoil unto the LORD and their riches 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; and as iron breaks in pieces and subdues all things, and as iron that breaks all these things, it shall break in pieces and bruise.
And whereas thou didst see the feet and toes, part of baked potters' clay and part of iron, the kingdom shall be divisive; but there shall be in it some of the strength of the iron, such as thou didst see the iron mixed with baked clay.
Iron sharpens iron; so a man sharpens the countenance of his friend.