Verse 5 said "va'Yomer Yirmeyah ha'Navi." Why is this repeated?
Mahari Kara: Yirmeyah answered Chananyah's words and prayed that they be fulfilled. He also explained the difference between Nevu'os for good and for evil (verses 7-9). Refer to 28:9:1:1-3.
Malbim: People misunderstood his intent; he needed to clarify his words. Refer to 28:6:2:4.
Why did he say "Amen Ken Ya'aseh"?
Rashi: May He do so!
Hagahah in Rashi and Radak, from Yalkut Shimoni 308: If only your words will be fulfilled - I will gain, and you will lose! I am a Kohen; I eat Kodshei Shamayim if the Bayis will remain standing. You are a Giv'oni 1 - "Asher mi'Giv'on" (verse 1). You will cut wood and draw water for the Mizbe'ach!
Hagahah in Rashi, citing Sotah 41b: If one flatters Shimon, he will eventually fall into Shimon's hands. If not, he will fall into the hands of Shimon's sons, or grandsons. We learn from Yirmeyahu, who supported Chananyah's false prophecy. Chananyah's grandson later seized Yirmeyahu and brought him to jail.
Malbim: This has two Perushim. (a) He wants his words to be fulfilled. (b) What you said is true. Hashem will fulfill your words to return the Kelim of Beis Hashem and all the exiles. Really, they will return, but not like you say, that it will be in two years. It will be after 70 years. The Kohanim and Am understood the first way. Yirmeyah needed to clarify that it will not be in two years.
Radak: According to the simple meaning, Chananyah was a Yisrael from Giv'on. The Giv'onim did not live in Giv'on from when it fell to Binyamin's inheritance.
What is the meaning of "Yakem"?
Rashi: This is a Tefilah (may He do so)!
