Jer. 21:4 'Thus says the LORD, the God of Israel: Behold, I will turn back the weapons of war that are in your hands and with which you are fighting against the king of Babylon and against the Chaldeans who are besieging you outside the walls. And I will bring them together into the midst of this city. 5 I myself will fight against you with outstretched hand and strong arm, in anger and in fury and in great wrath. 6 And I will strike down the inhabitants of this city, both man and beast. They shall die of a great pestilence.
I was just reading through this passage and WOW, I never want to be in this spot. The high priest had beaten Jeremiah and put him in stocks over night, because he didn't like what Jeremiah was saying, and this was God's answer to treating one of His prophets that way.
God obviously is serious about His children and He can back up His righteous anger.