Here God shows why he had formerly pronounced that they brought forward nothing but vanity and falsehood, namely, because they used his name falsely, and out of light created darkness; for by the feint of speaking in God's name, they darkened men's minds. That sacred name is, as it were, a fount of splendor, so as far to surpass the light of the sun; nay, whatever light exists, is made apparent and refulgent by it. But, as I have said, the servants of Satan turn light, into darkness, because they audaciously boast that God has said so. This passage and similar ones show us how diligently we ought to guard against Satan's fallacies. This is their astounding boldness to bring forward God's name while they so wantonly trifle with his judgments. For to boast that God has spoken is as if we wished, by impious profanation, purposely to draw him into a dispute. For how can God bear us to turn his truth into lie? But there have been impostors in all ages who have thus thoughtlessly flown in the face of God. We are not surprised at the heathen doing so; but in the chosen people, it was certainly an incredible prodigy and an intolerable disgrace, when they had access to all heavenly doctrine for the guidance of their conduct, and when God was daily calling forth prophets, as he had promised by Moses, to see these impious dogs who barked so, and you pretended so proudly to speak in God's name. (Deuteronomy 18:15-18.) Admonished, then, by this caution, let us be on our guard when we see Satan's servants endued with such arrogance. It follows --

Have ye not seen a vain vision, and have ye not spoken a lying divination, though (d) ye say, The LORD saith [it]; although I have not spoken?
(d) You promised peace to this people and now you see their destruction, so that it is revealed that you are false prophets.

Have ye not seen a vain vision,.... A vision only in pretence, and not in reality; the effect of their own fancy, and not anything shown them by the Lord:
and have ye not spoken a lying divination; delivered out a known lie, saying they had it from the Lord, when they had it not; or a prophecy that will deceive, and be without effect, and in the issue prove a falsehood:
whereas ye say, the Lord saith it; albeit I have not spoken? this is a proof that what they gave out for a vision and prophecy was a vain and false one; seeing they pretended they had it from the Lord, when he never spoke a word to them, or by them.