As much as the covenant promised great blessing, the consequence of breaking it is curses (Deuteronomy 28:1–68; Leviticus 26:1–46). So, the Lord finishes his appeal for repentance with a warning of the consequences if the people of Judah continue in their hard-hearted unfaithfulness that is seen outwardly in the evil of your deeds.
The Lord’s wrath will go forth like fire
that is unquenchable if Judah does not turn to him in repentance.
This last sentence also serves to prepare the reader for the next section in Jeremiah 4:5–6:30 which describes in more detail what the Lord’s judgment of Judah will be like. Even though Jeremiah is always urging Judah to repent, his overall expectation is that they will not do so, and that judgment is inevitable.
4 Circumcise yourselves to the LORD; remove the foreskin of your hearts, O men of Judah and inhabitants of Jerusalem; lest my wrath go forth like fire, and burn with none to quench it, because of the evil of your deeds.”