John Calvin Commentary Isaiah 36:5

"I say, [thy] counsel and strength for the war are but vain words: now on whom dost thou trust, that thou hast rebelled against me?" — Isaiah 36:5 (ASV)

I have said (only a word of the lips.) In the sacred history (2 Kings 18:20), the word used is, You have said. This may be explained as a declaration of what kind of courage Rabshakeh thinks Hezekiah possesses, as if he had said, “Such are your deliberations.” In this passage, the use of the first person, “I have said,” does not alter the sense, because Rabshakeh, as if he had examined Hezekiah’s counsels and fully understood them all, ironically reproaches him: “I see what you are thinking, but they are words of the lips.”

This passage is explained in various ways. Some interpret it as, “You say that you do not merely have words of the lips,” that is, “You boast that you excel not only in the use of words but also in courage and wisdom.” Others interpret it as, “You have words indeed, but wisdom and courage are necessary in war.”

Some think that by “words” are meant “prayers.” I do not approve of that interpretation, for it is excessively far-fetched and unnatural. Therefore, I view it as follows: “Hezekiah has words of lips, that is, he employs a beautiful and elegant style to keep the people in the discharge of their duty, or, as we commonly say, He has fine speeches; but it is not by these that war can be begun or carried on.” He therefore means that he perfectly understands what Hezekiah is doing and what it is on which he places his chief reliance—namely, on words and eloquence; but these are of no use for war, in which wisdom and courage are needed.

It might also be appropriately viewed as relating to the Egyptians, as if he had said that Hezekiah acts foolishly in allowing himself to be cheated by empty promises. Undoubtedly, the Egyptians were liberal in promising mountains of gold, though they gave nothing in reality. But as we will find that he speaks of the Egyptians soon afterward in a specific manner, I have no doubt that here he ridicules Hezekiah, as if he fed the people's expectations by empty boasting while he was not provided with military preparations.