What should they not fear?
Radak: Do not fear lest your leaving Galus will be like leaving other Galuyos. You encountered many afflictions in your land in Bayis Rishon 1 and Bayis Sheni.
Perhaps 'Bayis Rishon' includes from when they entered Eretz Yisrael until the first Churban. The eras when the Mishkan was in Nov, Giv'on and Shilo were closer to leaving Egypt than Bayis Rishon was! (PF)
Why does it say that you will not be ashamed?
Radak: After you leave this Galus, you will never have affliction. When a person rises to grandeur, and afterwards is lowered, he is ashamed.
What is "[Boshes] Alumayich"?
Rashi: Your youth.
Radak: The shame of your early days.
What is "Cherpas Almenusayich"?
Radak: The afflictions that you had in Galus, when you were like a widow. Amidst great good, you will forget the first afflictions - "Ki Nishkechu ha'Tzaros ha'Rishonos" (65:16).
Why is there another promise that you will not be ashamed?
Radak: After you will be in your land, you will not have shame.
Malbim: Before it mentioned Bushah, feeling ashamed by himself. Initially she was ashamed of her bad deeds - she was Mezanah under her husband, and served other gods. She did not have Kelimah (shame from others), for also others served idolatry, only when her Husband abandoned her. Hashem will pardon the first sins, ending the Bushah, and return her to Him, ending the Kelimah of widowhood. Here it does not say "Lo Tizkeri", for since it was recent, she cannot totally forget it.
