Isaiah 1:20

But if ye refuse and rebel, ye shall be devoured with the sword: for the mouth of the LORD hath spoken [it].

Ver. 20. But if ye refuse and rebel.] The Romans sent the Carthaginians caduceum et hastam, that they might take their choice of peace upon submission, or war upon refusal so to do. Similarily dealeth the Lord by this people here. Deu 30:19

Ye shall be devoured with the sword.] War is threatened, which is, saith one, the slaughter house of mankind, and the hell of this present world; and that we may not think that these are but big words, brute thunderbolts, it is added for confirmation,

For the mouth of the Lord hath spoken it.] Now whatsoever he hath spoken with his mouth, he will surely make good with his hand, as Solomon phraseth it in his prayer. The original hath it, "For the mouth of the Lord hath spoken" - q.d., Let his Word stand for a law with you. Justinian telleth us in his Institutes, that it was a prerogative belonging to the Roman emperor, Quicquid principi placuerit, legis habet vigorem, Whatsoever he pleased be bid be done was a law. And the French kings' edicts or proclamations always end with these binding words, Car bel est nostre plasir, For such is our pleasure, and we look to be obeyed. May not the King of kings say so much more?