What do we learn from "Yashvu la'Aretz [Yidmu Ziknei Bas Tziyon]"?
Nedarim 65a: Tzidkiyah saw Nevuchadnetzar eat a live hare. Nevuchadnetzar made him swear not to reveal this. Later, Tzidkiyahu rebelled 1 , i.e. he permitted his oath and revealed the matter. Nevuchadnetzar found out that the Sanhedrin improperly permitted the oath in his absence. He removed the pillows on which they were sitting; they were silent.
Rashi: They simply sat on the ground.
Rashi citing Eichah Rabah 2:14: Nebuchadnetzar summonsed the Sanhedrin. He recognized their esteem, and seated them on gold chairs. When he found out that they improperly permitted Tzidkiyah's oath (refer to 2:10:1:1), he commanded to remove the chairs and seat them on the ground. They tied them to horses via their hair, they were dragged around (Ri Kara - he decreed to kill them).
Ibn Ezra: Due to the lowering of the grandeur of Tziyon, the Zekenim sat on the earth in Galus.
Palgei Mayim: Due to Bitul Torah, Nebuchadnetzar seated the Sanhedrin on the ground.
Ri Kara: "Va'Yitfesu Es ha'Melech
What is the meaning of "Yidmu"?
Nedarim 65a: They were silent (refer to 2:10:1:1).
Rav Sadya Gaon: They are sad and mournful.
Why does it say "Horidu la'Aretz Roshan Besulos Yerushalayim"?
Rav Sadya Gaon, Ibn Ezra #1: They put their hair down to the ground 1 .
Ibn Ezra #2: They put their heads to the ground.
Ibn Ezra #3: Besulos do not rejoice at their Chupah.
Palgei Mayim: Besulos Yerushalayim are Tzadikim who never tasted sin. They were trapped in their sin; their heads were brought down to the ground, and they donned sackcloth.
Magihah (in Toras Chayim): I.e. they detached it.