God shews that it was the fault of the Jews, that he did not receive them into favor. And here he takes the argument from his own nature, and speaks of himself in the third person; and it is the same as though the Prophet had interposed this reasoning, "God is not inexorable, for he is as ready to forgive as he is long -- suffering: now, then, what prevents you from living happily again under his government? for he will spare you, provided he finds in you genuine repentance." We now then see, what the Prophet means here: for as God had kindly exhorted the people to repent, the Prophet speaks now generally of God's own nature, -- that he keeps not for ever, nor reserves perpetually These words, when put alone, mean that he does not cherish vengeance, and in our language we imitate the Hebrews, Il lui garde. This garde, when put without anything added to it, means, as I have said, that vengeance is cherished within. But nothing is more contrary than this to the nature of God. It hence follows, that the Jews had no obstacle in their way, except that they shunned God, and that being addicted to their own vices, they were unwilling to receive the pardon that was freely offered to them. As to the second clause, it admits of being explained in two ways. We may regard an adversative particle to be understood, "though thou hast spoken and hast done, "etc.; as if God had said, that he would be propitious to the Jews, however atrociously they might have sinned. But another view is more simple, -- that God here complains that there was no hope of amendment, as they had become hardened in their vices, "Thou hast spoken," he says, "thou hast done, and thou hast been able." And interpreters further vary in their views: for the copulative is explained by some as a particle of comparison, in the sense of k'sr, keasher, "according to what thou wert able, thou hast done wickedness." But others take the words more simply and more correctly, as I think, "Thou hast been very strong;" that is, thou hast exerted all thy power, so that thou hast put forth all thy strength in doing evil, as we say in Latin, pro virili, with all thy might; that is, as far as thy capacity extended, thou hast devoted thyself to wickedness. [1] I therefore give this explanation: God had before put on, as it were, the character of one in grief and sorrow, and kindly exhorted the people to repent, and testified that he would be ready to pardon them, and at the same time shewed in general that he would be propitious, as he is by nature inclined to mercy. After having set forth these things, he now adds, that he despaired of that people, because they gloried in their own wickedness: for to speak and to do means the same as if he had said, that the people were so impudent, that they boasted of their rebellion against God, and dared to call darkness light; for the superstitious, we know, glory against God without any shame. Now, such was the state of the people; for God, by his prophets, condemned this especially in them -- that they had corrupted the pure worship of the law; but they with a meretricious front dared to set up against him their own devotions and good intentions, as they are commonly called. As then, they thus presumptuously defended their wicked deeds, God here complains that they were in no way healable, and so he leaves them as past remedy. This I regard as the real meaning of the Prophet: and of similar import is the verb tvkl, tucal; "thou hast put forth all thy might," he says, that is, thou hast observed no limits in sinning, but, on the contrary, hast given thyself up to unbridled licentiousness. It now follows --

Footnotes

1 - This and the preceding verse have been variously explained. The view given by Calvin has been most commonly adopted; but it is hardly consistent with a literal rendering of the original, which I consider to be as follows, -- 4. Hast thou not from this time called to me, "My Father, the guide of my youth art thou: 5. Will he reserve wrath for ever, Or keep it to the end?" Behold, thou hast so spoken, And hast done evils and persevered. "From this time," that is, the time spoken of before, when the people followed idolatry. During this time, they called God their Father, and promised themselves the remittance of his displeasure. They said this, and yet followed their superstitions. This is the view which Gataker seemed most disposed to take. Horsley thus paraphrases the last line, -- "Thou hast persisted incorrigibly in doing evil." The Septuagint give "called," in the past tense; the Vulgate, in the imperative, "voca -- call;" the Syriac, the Arabic, and the Targum, in the future tense, "Wilt thou not call," etc. The received text has qr'ty, which is no doubt wrong; the iod is not found in very many MSS., and all the early versions agree in giving the verb in the second person. The same is to be said of dvrty, it ought to be dvrt, though Horsley prefers the former; but neither the early versions nor the context favor it. The phrase mth is rendered by the Septuagint, "hos oikon -- as a house," and by the Arabic, "ut filia -- as a daughter." How such mistakes could have been made, it is difficult to say. The Syriac has "hereafter;" and the Targum, "from this time." -- Ed

Rather, "Will he, the young husband," retain, "keep up His anger forever!" These words should be joined to Jeremiah 3:4.
Behold - Rather, "Behold, thou hast spoken" thus, but thou hast "done evil things" persistently. The King James Version translates as if Judah's words and deeds were both evil. Really her words were fair, but her deeds proved them to be false.
And here ends the prophecy, most interesting as showing what was the general nature of Jeremiah's exhortations to his countrymen, during the 14 years of Josiah's reign. He sets before them God and Israel united by a covenant of marriage, to the conditions of which Yahweh is ever true, while Israel practices with zest every form of idolatry. Therefore, the divine blessing is withheld. It is an honest and manly warning, and the great lesson it teaches us is, that with God nothing avails but a real and heartfelt repentance followed by a life of holiness and sincere devotion to His service.
Jeremiah. 3:6-4:4 - "The Call to Repentance"
The former prophecy ended with the denunciation of God's perpetual anger because of Israel's obstinate persistence in sin. Now there is an invitation to repentance, and the assurance of forgiveness. The argument is as follows: Israel had been guilty of apostasy, and therefore God bad put her away. Unwarned by this example her more guilty sister Judah persists in the same sins Jeremiah 3:6-11. Israel therefore is invited to, return to the marriage-covenant by repentance Jeremiah 3:12-14, in which case she and Judah, accepted upon the like condition, shall become joint members of a spiritual theocracy. Jeremiah 3:15-18. The repentance which God requires must be real Jeremiah. 3:19-4:4.

Will he reserve his anger for ever? - Why should not wrath be continued against thee, as thou continuest transgression against the Lord?

Will he reserve his anger for ever?.... These words may be considered as a continuation of the speech put into their mouths to make to the Lord and plead with him, as well as what follows:
will he keep it to the end? that is, his anger: no; he will not: this is not according to the nature of God; he retains not his anger for ever, Micah 7:18, though, according to some versions, this is to be understood of the sins of these people being reserved and kept forever, as their impudence and obstinacy; so the Syriac and Arabic versions; and to which agrees the Targum,
"is it possible that thy sins should be kept for thee for ever, or the stroke (of punishment) be strengthened upon thee to the end?''
so Kimchi,
"says the prophet, if thou dost this (call him my father, &c.) will God reserve thine iniquity for thee for ever, or keep thy sin unto the end? he will not do so; but when thou returnest unto him, he will return unto thee, and do thee good; but thou hast not done so.''
The sense is much the same:
behold, thou hast spoken, and done evil things as thou couldest; which were enough to cause the Lord to reserve and keep his anger for ever. There is a double reading here; the Cetib, or writing, is "I have spoken"; the prophet had spoken to them to return; or the Lord by the prophet had spoken to them, and put the above words into their mouths, and told them what they should say when they returned to the Lord; "but thou hast done evil things" (y); notwithstanding such declarations of grace, and dost continue to do them:
and thou hast prevailed (z); as the last clause may be rendered; that I cannot turn away mine anger from thee, but must reserve it, and keep it for ever. The Keri, or reading, is "thou hast spoken"; thou hast said thou wilt do evil things, and thou hast done them as thou hast said, and hast prevailed; thou hast sinned with all thy might and main, and hast spoken and done as evil things as possibly could be done. Some choose to render the words thus, "if thou hadst spoken"; the words that were put into their mouths before mentioned; "though thou hast done evil things, yet thou wouldest have prevailed" (a); that is, with God, to have turned away his anger from thee.
(y) "sed fecisit mala", Schmidt. (z) "et praevaluisti", Vatablus, Schmidt; "et preavales", Piscator, Gataker; "et evaluisti", Cocceius. (a) "Si ita loquereris, quanquam mala plurirma fecisti, praevaleres", Grotius.

he--"thou," the second person, had preceded. The change to the third person implies a putting away of God to a greater distance from them; instead of repenting and forsaking their idols, they merely deprecate the continuance of their punishment. Jeremiah 3:12 and Psalm 103:9, answer their question in the event of their penitence.
spoken and--rather (God's reply to them), "Thou hast spoken (thus), and yet (all the while) thou hast done evil," &c.
as thou couldest--with all thy might; with incorrigible persistency [CALVIN].

Will he - Will he not be reconciled?