John Calvin Commentary Jeremiah 5:20-21

"Declare ye this in the house of Jacob, and publish it in Judah, saying, Hear now this, O foolish people, and without understanding; that have eyes, and see not; that have ears, and hear not:" — Jeremiah 5:20-21 (ASV)

The Prophet confirms what he had said, so that the Jews would not think that they were only terrified by words, and not dread the consequences. Therefore he says, Declare this. The Prophet, no doubt, alludes to a custom that was common, for wars were usually proclaimed by heralds. Enemies did not immediately march out, but they proclaimed war so that the cause might appear just. Therefore God here declares that he had spoken in earnest by the mouth of Jeremiah, as though war had been proclaimed in the usual manner, and armed enemies were already near.

Declare you then this; and what is it? Hear, O foolish people, etc. Here he first rebukes the Jews and Israelites for their stupidity, because they were even without common sense; for the heart in Hebrew means the mind or understanding, as we have seen elsewhere. He then says that this people were destitute of all understanding. He first calls them fatuous or foolish; but as many are slow and heavy and yet not without common sense, he adds that they were a people without heart or understanding. He seems indeed to add by way of correction that they had eyes and ears, but his object was ironically to enhance what he had said and to show that they were stupid, and no less so than blocks of wood or stones. How so? You have ears and eyes, he says, but you neither see nor hear.

He no doubt alludes to the idols to which they had become devoted: for it is said in Psalm 115:8, that those who made idols were like them, as well as those who trusted in them; for it had been previously said that idols had ears but heard not, and eyes but saw not. Jeremiah then indirectly condemns the Jews here for having become so stupid in their superstitions as to be like dead idols: for there is in an idol some likeness to man; it has various members but no understanding. So also he says, the Jews had eyes and ears and the external form of men; but they were at the same time no less stupid than if they were stones or blocks of wood. Now follows the proclamation —