Daniel 2:40
"And the fourth kingdom shall be strong as iron: forasmuch as iron breaketh in pieces and subdueth all things: and as iron that breaketh all these, shall it break in pieces and bruise."
Cross References (ranked by relevance)
After this I saw in the night visions, and behold a fourth beast, dreadful and terrible, and strong exceedingly; and it had great iron teeth: it devoured and brake in pieces, and stamped the residue with the feet of it: and it was diverse from all the beasts that were before it; and it had ten horns.
Shall iron break the northern iron and the steel?
And after threescore and two weeks shall Messiah be cut off, but not for himself: and the people of the prince that shall come shall destroy the city and the sanctuary; and the end thereof shall be with a flood, and unto the end of the war desolations are determined.
Thus saith the LORD; For three transgressions of Damascus, and for four, I will not turn away the punishment thereof; because they have threshed Gilead with threshing instruments of iron:
And his power shall be mighty, but not by his own power: and he shall destroy wonderfully, and shall prosper, and practise, and shall destroy the mighty and the holy people.
If we let him thus alone, all men will believe on him: and the Romans shall come and take away both our place and nation.
His legs of iron, his feet part of iron and part of clay.