God wants the Israelites to swear a loyalty oath that will involve circumcising their hearts. Ouch! And the consequences for not doing so will be even more painful: burning to death. He also promises to reenact his little temper tantrum at Sodom and Gomorra in a few cities in the north, as well as the royal family. He will do all this in the form of a thunderstorm. But unlike the first case, the people will survive this one and will run out to the desert, where the heat and wind and dry air will ruin their skin and no one will want to have sex with them anymore. And in the final verse, Jeremiah proves that he's just as childbirth-obsessed as Isaiah, predicting the resulting wailing will be like a woman in labour with her first child.
God says he'll refrain from destroying Jerusalem if he can find even one man who is blameless. It turns out all that smiting and plaguing and burning people alive has not had the intended effect. I'm shocked. SHOCKED. But of course god doesn't think it's his insane methodology that's at fault, the people are clearly poor and dumb. So he decided to go and talk to the rich people, who are clearly smarter, and found the same thing. Now he's planning to send lions, leopards and wolves to kill them. What's that they say about the definition of crazy being 'Someone who does the same thing over and over again and expects a different result every time?' Yeah, that's what this is.
No, he just can't forgive them because they've committed adultery and visited prostitutes. They've also decided that god doesn't exist, so he has to burn them to death now. And then he's going to send strangers in to take over their property. But he promises not to starve them to death. He ends the chapter by showing just a bit too much of his hand: The prophets prophesy falsely (v. 33).
At this point, we've gone through 72 straight chapters of god's bipolar disorder, in which he alternately lavishes attention and empty promises on the Israelites, then threatens them with creative new forms of destruction. So I'm going to try and get through Jeremiah 3 chapters at a time, though I have very low hopes for the rest of the Old Testament. There's a reason you've never heard of Obadiah, Amos or Joel.
Anyway, god instructs the Benjaminites to prepare themselves for war against the rest of the tribes, starting with Jerusalem. Why? Because they haven't circumcised their ears. So he has to kill all of them, and the Benjaminites will get to scavenge. He'll do this after deliberately making them sin. So why not make them obey?