What is the meaning of "v'Sicheisi"?
Rashi: I will uproot. This is like "Beis Ge'im Yisach Hashem" (Mishlei 15:25), "v'Nisachtem me'Al ha'Adamah" (Devarim 28:63).
Radak: It was built in a rock in the sea. It was covered with earth in order to settle it. When the sea covered it at the time of its Churban, the earth was cast off, and the rock was dry, like initially.
Malbim: I will remove the earth that blocks the sea, and the sea will flood [Tzor] when it rises, and only a rock will remain, which not proper for settlement.
Why are "v'Shichaso" and "v'Harsu" third person plural, and "v'Sicheisi" is first person singular?
Malbim: The enemies will destroy the walls and towers; I will remove the earth, and the rock will be smooth.
What is the comparison to "Tzechi'ach Sela"?
Rashi: It was built in a rock in the sea. When it is dismantled, and the earth will depart to the sea, the rock will remain smooth. So Yonason translates.
Radak: This is the peak of a rock. It is called so for it is the dry part. Also "Shachnu Tzechichah" (Tehilim 68:7) is a dry place.
