To whom is "Al Tismechi Oyavti" said?
Rashi: This refers to Bavel and Romi 1 , which is liable.
Radak: Perhaps the Yud at the end of Oyavti is a pronoun (my enemy), even though it is mi'L'eil (the penultimate syllable is accented). It refers to the kingdom that has ruled over Yisrael for more than 1000 years 2 .
Why does it say "Al Tismechi"?
Radak: [Yisrael's captor] thinks that Yisrael's hope is lost, and rejoices over their demise. He tells her not to rejoice. Targum Yonasan is like this.
Malbim: Do not rejoice that I am in Galus, for via falling to the depth of the pit, I will rise and be encouraged, for via this I will be saved.
What do we learn from "Ki Nafalti Kamti"?
Radak: If I fell in Galus, I will rise again. Kamti is past tense used in place of future; this is common in Nevu'ah, for what Hashem says will be, it is as if it [already] came.
What is the meaning of "Ki Eshev ba'Choshech Hashem Ohr Li"?
Radak: If I dwell in Galus in darkness, i.e. in great affliction, which is compared to darkness, I trust that Hashem will still be light for me, and take me out from darkness to light.
Malbim: If I do not have physical light (success), I have Hashem's light ? creed and Emunah, the light of hope in His salvation.


