20. The anger of the LORD shall not return, until he have executed, and till he have performed the thoughts of his heart: in the latter days ye shall consider it perfectly.
20. Non revertetur iracundia Jehovae usque dum fecerit, et usque dum stabilierit cogitationes cordis sui: in extremitate dierum intelligetis hoc intelligentia (hoc est, intelligetis hujus rei intelligentiam, ad verbum.)
He confirms what he had said, lest the hypocrites, with whom he had to do, should think that their punishment would be light and soon pass away. For though they may have seen that God's hand was armed against them, yet they took comfort, because they expected that it would only be for a short time. Hence Jeremiah here reminds them that they were much deceived if they thought that they could dissipate as a cloud the vengeance that, was at hand; for God would not cease to punish them until he had destroyed them.
There was another security which deceived the ungodly: they were not terrified by threatenings of the Prophet, because they thought that God was in a manner dallying with them whenever he denounced ruin. And, doubtless, the wicked could not have so securely indulged themselves, had it not been that they did not believe that God's word would be fulfilled. As, then, God's threatenings did not strike hypocrites with terror, the Prophet here declares that there was no reason for them to harbor the vain hope that God only uttered words, and that there would be no execution of his vengeance.
Turn back, he says, shall not the anger of Jehovah until he has performed and confirmed the thoughts of his heart Jeremiah shews that God had not spoken in vain by his servants, according to what is done by men, who often speak rashly, for their tongue frequently outruns their purpose. But he reminds them here that God is far different from men, for he ever speaks in earnest, and his prophetic word is a sure evidence of his hidden purpose, as it will again be presently declared. This is the reason why he mentions the thoughts of his heart
We must not yet think that God is like us, as though he reflected on this thing and on that, and formed many purposes, while one thing or another comes into his mind; no, such a gross idea as this cannot be entertained, and cannot be consistent with the nature of God.
But Jeremiah calls, by a kind of metaphor, the counsel of God his thoughts, even that fixed and unchangeable counsel, which he declared by his prophets. Sometimes, indeed, God threatened, in order to restore men to repentance; but we must bear in mind that he neither varies himself nor changes his purpose. Whatever, then, the prophets announced in his name, flowed from his hidden purpose, and it was the same as though he had made known to us his own heart. And it is no small commendation to prophetic doctrine that God as it were connected his heart with his mouth. The mouth of God is the doctrine itself; and he says now that it had proceeded from the depth of his heart. It hence follows that there is nothing frustratory, (deceptive,) as they say, in God's word; for he here declares that whatever he had committed to his servants were the thoughts of his heart. And to confirm, or establish, must be applied to the execution of his thoughts.
The sum of the whole is, that God now pronounces a sentence against the people, which could not be reversed; for he had once for all decreed to destroy the men who were obstinate in their sins.
But he seems to refer to the word ychvl, ichul, which means, as I have said, to fall, and also to abide or to lie upon. According to this meaning, he says now, that the anger of God would not return, so as to change its course, until it had completed what had already been decreed, even what God had resolved respecting the destruction of the people.
Then he adds, In the extremity of days ye shall understand the knowledge of this thing So it is literally; but we may give a simpler version, "Ye shall perceive the knowledge of this matter," or "Ye shall know what this means." The Prophet, no doubt, exults over the insensibility of those who could not be moved by such awful warnings. We know how great is the hardness of the ungodly, especially when Satan possesses their minds and hearts. There is, indeed, no iron and no stone which has so much hardness as there is in the perversely wicked; and they in a manner assail God with the greatest obstinacy, as though they were victorious, for they despise all his warnings and threatenings. Hence the Prophet derides their insolence, or rather their madness, and. says, "Ye shall understand," but too late; for by extremity of days,  he means the time which God had appointed for his anger. But yet God had in due time warned them that they might repent before his judgment came. It was now then the same as though he left them in their own stupor, and said that they could not, however, escape the hand of God by their perverseness, according to what Paul says,
"Let him who is ignorant, be ignorant."
He no doubt checks the arrogance of those who rejected every sound doctrine and all right counsels.
So, then, the Prophet teaches us here that hypocrites gain nothing by setting up their own contumacy and arrogance in opposition to God, for they will find, though too late, that God has not spoken in vain. We then see that by extremity of days is to be understood that time when the door shall be closed, because they did not in due time respond to God when he invited them to himself, and set before them the hope of salvation.
There is also another truth taught us here, that we are to seek God while he may be found, and call upon him while he is near. (Isaiah 55:6.) For if we abuse his forbearance and despise him who speaks to us today, we shall find out too late, and not without the most grievous sorrow, that we have been deceived by the devil, because we did not attend to God calling us. It follows, —
 Literally, "at the posteriority of days," meaning, at a future time, without designating any particular period; it is the same as "hereafter." The words which follow can hardly be rendered literally in our language -- "ye shall discern it with discernment." What is the antecedent to "it," which is, h, a feminine gender? Venema says that it is to be taken as a neuter; but if so, what does it refer to? It appears to me that there is nothing in the passage to which it can be referred, except to the "tempest," which is feminine, in the former verse; they would understand at a future time the meaning of that tempest, that it was from the Lord as a punishment for their sins. This they did not understand at the time. These two verses are found nearly in the same words at the end of Jeremiah 23:30: The last word is omitted there, -- "At the posteriority of days ye shall discern it," or understand it, or consider it. The Vulg. here is, "at the last days ye shall understand his counsel;" the Sept., "at the last of days ye shall understand it;" and the Targ., "at the end of days ye shall by understanding understand this."