Ibn Ezra on Isaiah

They are in meaning the same, although the one contains some additional words, which the other has not; the words may be compared with instruments, their meanings with the workmen. I shall now explain six passages.

1. In the book of Kings (18:20) Thou sayest (but they are but vain words) I have counsel and strength for war; that is, thou hast said to thy people, that thou hast wisdom and strength for war, but this was only a word of the lips, thy strength consisted only in words. In the book of Isaiah (36:5) it is said, I say but vain words are counsel and strength for war. These are the words of Rabshakeh; he says: I believe, that thy counsel and strength for war consist only in words.