What fire came out of Mateh Vadeha?
Rashi: This evil came to them due to the sin of their king and officers.
Radak: The Churban; Tzidkiyah caused it.
Malbim: This is the fire of Yishmael ben Nesanyah. He was Mateh Vadeha, i.e. from the royal seed.
Why does it say "v'Lo Hayah Vah Mateh Oz Shevet Limshol"?
Radak: After Tzidkiyah, there was no strong staff to rule.
Malbim: After Gedalyah was killed, all authority over the land ceased.
What is the meaning of "Kinah Hi va'Tehi l'Kinah"?
Rashi citing Targum Yonasan: The Nevu'ah is lamentation, and it will be lamentation.
Radak: It was lamentation in the Nevu'ah, and it will be lamentation at the time of the Churban and Galus.