John Calvin Commentary Jeremiah 15:12

"Can one break iron, even iron from the north, and brass?" — Jeremiah 15:12 (ASV)

This verse has also been interpreted in different ways. Some take the word iron, when repeated in a different case, to mean, “Will iron break iron?” But others think the subject is missing from the clause and understand “people” to be implied: “Will the Jews break the iron, even the iron from the north—and not only the iron but the brass also, or, the brass mixed with iron?” In reality, the difference is only in words.

If we read, “Will the iron break the iron from the north?” the meaning will be this: “Though there is great hardness in you, can it still break that which is in the Assyrians? But you are not equal to them. Make your strength as great as you wish; the Chaldeans will still be harder and will break you. For if you are iron, they are brass or steel, and so you will not be able to sustain their violent attacks.”

As the Prophet’s meaning is sufficiently evident, I will not insist on words, though the rendering I most approve is this: “Will iron break the iron (the repetition is emphatic) from the north and the brass?”

Here we also see that the holy man’s design was to strip the Jews of that false confidence in which they boasted. For why were they so stubborn, if not because they did not fear any misfortune? Since they were then secure, predictions had little weight with them. Hence the Prophet, to beat down this ferocity, says that there would be greater hardness in the Chaldeans, for they would be like iron, and indeed steel also.