Daniel 2:33
its legs of iron, its feet part of iron, and part of clay.
Daniel 2:40-43
And the fourth kingdom shall be strong as iron, forasmuch as iron breaketh in pieces and subdueth all things; and as iron that crusheth all these, shall it break in pieces and crush.
Daniel 7:7-8
After this I saw in the night-visions, and, behold, a fourth beast, terrible and powerful, and strong exceedingly; and it had great iron teeth; it devoured and brake in pieces, and stamped the residue with its feet: and it was diverse from all the beasts that were before it; and it had ten horns.
Daniel 7:19-26
Then I desired to know the truth concerning the fourth beast, which was diverse from all of them, exceeding terrible, whose teeth were of iron, and its nails of brass; which devoured, brake in pieces, and stamped the residue with its feet;