John Calvin Commentary Jeremiah 36:31

"And I will punish him and his seed and his servants for their iniquity; and I will bring upon them, and upon the inhabitants of Jerusalem, and upon the men of Judah, all the evil that I have pronounced against them, but they hearkened not." — Jeremiah 36:31 (ASV)

Here a reason is given for what the previous verse contains. If the Prophet had only said that the king's dead body would remain unburied and cast out in dishonor, exposed to the cold by night and the heat by day, the narrative would not have produced the intended effect. But God here shows the cause: He had forewarned King Jehoiakim, all his counsellors (called servants here), the inhabitants of Jerusalem, and all the Jews universally.

Since they had then been clearly told in due time what calamity was near at hand, and yet no one had repented, God now says that for this great obstinacy He would take vengeance: I will visit him and his descendants and the whole people for their iniquity. What was this iniquity? Namely, that they had so grievously and in so many ways provoked God, and had not returned to a sound mind, though reproved by the Prophet, but had instead become more and more hardened.

The Prophet thus points out the extremity of their iniquity: they did not listen to the warnings by which God had endeavored to rescue them from the coming ruin. For there would have been some hope of deliverance if they had sought to avert God’s wrath; but since His warnings had been despised, it was, as I have said, an extreme iniquity. And we see elsewhere how much God abominates this diabolical presumption of men:

“I have called to sackcloth and ashes; but you have called to the harp and to joy, and have said, ‘Let us feast and drink, for tomorrow we shall die:’ As I live, this iniquity shall not be blotted out” (Isaiah 22:12–13).

God swore by Himself that this sin would not be expiated, because the Jews did not repent when He kindly invited them to Himself and declared to them that they could not escape extreme punishment. It is therefore no wonder that God here also represents their obstinate wickedness as being the greatest, since the Jews did not listen to the reproofs conveyed to them by the mouth of Jeremiah.