26. How long shall this be in the heart of the prophets that prophesy lies? yea, they are prophets of the deceit of their own heart;
26. Quosque erit in corde prophetarum prophetantium mendacium, et prophetarum doli cordis sui?
27. Which think to cause my people to forget my name by their dreams which they tell every man to his neighbour, as their fathers have forgotten my name for Baal.
27. Cogitantes ut faciant oblivisci populum meum nominis mei per somnia sua (vel, in somniis suis, ad verbum,) qua narrant quisque socio suo; quemadmodum obliti sunt patres eorum nominis mei in Baal.
Here God reproves the false prophets, and also promises to his people what was especially to be desired, — that he would cleanse his Church from such pollutions. He then shews that it was his purpose to take vengeance, because the false prophets had dared in such an impious and bold manner to abuse his sacred name. For it ever occurred to their minds, "How is it that God permits this? Is it because he cares not for the safety of his people? or does it give him any delight when he sees truth mingled with falsehood, and light with darkness?" Hence God here shews that he for a time bore with that sacrilegious audacity which the false prophets practiced, but that he did not so connive at it as not at length to punish them.
How long? he says, which is the same as though he had said, "It shall not be perpetual; though I may delay, yet they shall know that they have with extreme perverseness abused my forbearance." And he also enhances their crime by saying, How long shall it be in the heart of the prophets to prophesy falsehood? By this way of speaking he intimates, that they erred not through ignorance, as many do, who through want of knowledge bring forth what they do not understand; but God here complains that these prophets, as it were designedly, rose up to suppress the truth. Then by heart is to be understood thought or purpose; as though he had said, that they designedly made a false pretense as to his name, that it was their settled purpose to deceive the people. 
He adds, that they were prophets of the deceit of their own heart. This deceit of the heart is put in opposition to true doctrine; and thus God intimates that whatever men bring forward from themselves is deceitful, for nothing can proceed from them but vanity. There is yet no doubt but that he condemns that foolish conceit, of which the false prophets proudly boasted, that they were alone wise, as the case is now under the Papacy; how arrogantly do unprincipled men prattle whenever they speak of their own figments? Nothing can be more silly, and yet they think that they surpass the angels in acuteness and in high speculations. Such was the arrogance displayed by the false prophets of old. But God declares that whatever men invent, and whatever they devise, which they have not received from his mouth, is only the deceit of the heart.
And this ought to be carefully noticed; for there are many plausible refinements, in which there is nothing solid, but they are mere trifles. If, then, at any time these vain thoughts seem pleasing to us, let us bear in mind what Jeremiah says here, that whatever proceeds not from God is the deceit of the heart; and further, that though the whole world applaud falsehoods and impostures, we ought yet to know that everything is a deceit which has not God himself as its author.
Then follows a clearer definition, that they made his people to forget his name by their dreams, as their fathers had forgotten it through Baal.  We may infer from this verse, that those with whom Jeremiah contended were not openly the enemies of the Law; for they held many principles of true religion. They maintained in common with the true and sincere worshippers of God this truth, — that the only true God ought to be worshipped; and also this, — that there was only one legitimate altar on which sacrifices according to the Law were to be offered. On these points, then, there was no controversy. But yet they deceived the people by their flatteries; for they made gain of their prophetic office. Hence Jeremiah condemns them, because they made God's name to be forgotten by their dreams, as their fathers had forgotten it through Baal; as though he had said, "These dreams are like the fictitious and spurious forms of worship, by which true religion was formerly subverted; for their fathers worshipped Baal and Baalim: they set up for themselves these false gods, and thus subverted the glory of God by their own devices." The impiety of the false prophets, who lived in the time of Jeremiah, was not indeed so gross; and yet it was an indirect defection, for they brought forward their dreams, and falsely professed that. they were God's servants, though he had not commissioned them.
We have said elsewhere (Jeremiah 23:21) that their crime was twofold; first, they ran when not called nor sent; and secondly, they brought forward their own fancies and not the word of God. And this passage ought to be carefully noticed; for we here learn, that not only open defection cannot be endured by God, but also indirect depravations, which stealthily withdraw us from the fear of God. Then these two evils must be carefully avoided in the Church, if we desire to continue entire in our obedience to God. One evil is sufficiently known, that is, when truth is openly turned into falsehood, when men are drawn away into idolatry and filthy superstitions, or when the ancient people, as Jeremiah says, forgat the name of God through Baal. But the other evil is more hidden, and therefore more dangerous, that is, when some appearance of true religion is retained, and men are yet insidiously drawn away from the fear of God and his true worship, and from pure doctrine, as we see to be the case at this day in the Churches, which profess to have separated from the Papacy that they might embrace the doctrine of the Gospel: there are many among them who insidiously corrupt the simple and genuine doctrine of the Gospel. We see how many curious men there are at this time, who disturb all things by their own inventions, and how absurdly many seek refinements, and how confidently also do many propound their own inventions as oracles! It behoves us then to be watchful, not only that we may shun open abominations, but that we may also retain the pure and true word of God, so as not to allow false workers insidiously to corrupt and vitiate anything. It follows, —
 Emendators have been very busy in correcting the first words in this verse, without the authority of any MSS., or of the early versions. When there is a meaning and a striking one, emendations, merely conjectural, are surely to be repudiated. Houbigant, Blayney, and Horsley, have their corrections, but we can do without them. What seems to have prompted conjectural emendations has been the h prefixed to ys; but Gataker removed this difficulty; his version is substantially as follows, -- How long! -- Is it in the heart of these prophets, To be prophesying falsehood, And prophesying the deceit of their own hearts? To be "in the heart" is to be resolved, to form a purpose or determination. See Isaiah 63:4. It is the same, as though it was said, "Are these prophets resolved?" To be "in the heart" means also to delight in a thing. See Psalm 40:8. The meaning then may be, "Is it the delight of these prophets?" etc. But the first sense is the most suitable. "How long!" is an exclamation of wonder at their perseverance in their wicked course. They had been often warned, and yet they continued. Then follows a question, whether it was their settled purpose to persevere in prophesying falsely? -- Ed.  Calvin begins this verse as our version, "Who think," etc. So the Sept.; the Vulg. is, "who seek (or wish), volunt." Blayney has, "who study." The verb means sometimes to contrive or to purpose a thing after counting the reasons for and against. It may be rendered here, "who design." The Syriac is, "whose counsel is." It was their design and intended object to make the people to forget God's name through their dreams. But how to forget his name? for they professed to announce their dreams in his name. God's name here evidently means his revealed name, himself as revealed in his word. -- Ed
 Calvin begins this verse as our version, "Who think," etc. So the Sept.; the Vulg. is, "who seek (or wish), volunt." Blayney has, "who study." The verb means sometimes to contrive or to purpose a thing after counting the reasons for and against. It may be rendered here, "who design." The Syriac is, "whose counsel is." It was their design and intended object to make the people to forget God's name through their dreams. But how to forget his name? for they professed to announce their dreams in his name. God's name here evidently means his revealed name, himself as revealed in his word. -- Ed