'Iron' in the Bible

And Jehovah was with Judah; and drove out the inhabitants of the hill-country; for he could not drive out the inhabitants of the valley, because they had chariots of iron.

And the children of Israel cried unto Jehovah: for he had nine hundred chariots of iron; and twenty years he mightily oppressed the children of Israel.

And Sisera gathered together all his chariots, even nine hundred chariots of iron, and all the people that were with him, from Harosheth of the Gentiles, unto the river Kishon.