What is the meaning of "Al Tihyeh Li li'Mechitah"?
Rashi: Your Shelichus should not be for me ruin.
Malbim: I prayed to delay the punishments - this should not be my ruin, that they will clarify 1 that I am a false Navi.
Normally, if a Nevu'ah for evil is not fulfilled, this does not discredit the Navi. Perhaps people repented, and Hashem retracted! Malbim wrote above (4:28) that the decree for the Churban was unlike other decrees; it was absolute without regret, even if they would improve their deeds. However, refer to 17:21:2:2! (PF)
What is the meaning of "Machsi Atah b'Yom Ra'ah"?
Radak: On a day that they intend evil for me, You are my refuge. You always do so, so I will not fear them, like You promised.
