John Calvin on Jeremiah 3:20

He confirms the first clause of the preceding verse: for he had said that it could hardly be that the Jews would recover what they had lost, and be formed again a new people; and he shews the reason, — because they were like an adulteress, as he had before stated. But he did not yet wish to take away every hope; only he insists on this, that they were seriously to consider their sins, in order that they might become displeased with themsalves, and flee to God’s mercy for refuge. Nor did he do this so much for their sake, as for the sake of the people among whom he dwelt. For he had respect, as it has been often stated, especially to the Jews, who had become so hardened in their vices as not to think that this example, by which God intended to terrify them, so as to bend their hard hearts to repentance, belonged to them. Hence it was for this reason that God so severely reproved Israel; for he had said before, that the Jews were still worse. He afterwards subjoins —

Jeremiah 3:21

21. A voice was heard upon the high places, weeping and supplications of the children of Israel: for they have perverted their way, and they have forgotten the LORD their God.

21. Vox super excelsa audita est, fletus precationum filiorum Israel; quia perverterunt viam suam, obliti sunt Jehovae Dei sui.