John Gill's Exposition of the Whole Bible
Isaiah 36:5
I say, (sayest thou,) but they are but vain words,.... Or, "word of lips" f; meaning the following, which he suggests were only the fruit of his lips, not of his heart; or were vain and foolish, and without effect, and stood for nothing; so the first part of the words are Hezekiah's, "I say (sayest thou)"; and the latter, Rabshakeh's note upon them; though they may be understood as Hezekiah's, or what he is made to speak by Rabshakeh, as the ground of his confidence, namely, "word of lips"; that is, prayer to God, as Kimchi explains it; or eloquence in addressing his soldiers, and encouraging them to fight, either of which Rabshakeh derides, as well as what follows:
I have counsel and strength for war; as he had; he had wise ministers to consult, and was capable of forming a good plan, and wise schemes, and of putting them in execution, and of heartening men; though he did not put his confidence in these things, as Rabshakeh suggested,
2 Chronicles 32:3, the words may be rendered; "but counsel and strength are for war" g: what signifies words to God, or eloquence with men? this is all lip labour, and of little service; wisdom and counsel to form plans, and power to execute them, are the things which are necessary to carry on a war with success, and which, it is intimated, were wanting in Hezekiah; and therefore he had nothing to ground his confidence upon, within himself, or his people:
now on whom dost thou trust, that thou rebellest against me? which it does not appear he had, having paid the money agreed to for the withdrawment of his army; but this was a pretence for the siege of Jerusalem.
f דבר שפתים "verbum labiorum", Montanus; "vel, sermo labiorum", Vatablus. g עצה וגבורה למלחמה "consilium et fortitudo ad praelium", Montanus; "sed consilio et fortitudine opus ad praelium", Pagninus, i.e. "requiruntur", ut Grotius.