What is the meaning of "bi'Rtzonecha He'emadta l'Hareri Oz"?
Rashi: When You wanted, You made my mountain (grandeur) strong.
Radak: As long as Your desire was with me, my intellect was strong. My Yetzer ha'Ra could not take it from me. It is as if it says b'Oz; the Beis is omitted. Alternatively, Oz is an adjective, like "Lechem Chom" (Shmuel I, 21:7), "Ma'oz la'Tom" (Mishlei 10:29).
Malbim: My mountain (life of my body) stood on Your desire. The moment You hid Your face from me, the mountain began to falter, for its foundation lapsed. My illness was not via active Hashgachah; just via hiding Your face and removal of Hashgachah.
Why did he say "Histarta Fanecha Hayisi Nivhal"?
Radak: The moment You hid Your face from me, and did not help my intellect - either to test me, because I prided myself, or for a punishment for a prior sin - I stumbled, and my Yetzer ha'Ra overpowered my intellect. This is why David prayed "Gam mi'Zedim Chashoch Avdecha Al Yimshelu Vi", like I explained (refer to 19:14:2:2).
Malbim: Refer to 30:8:1:3.
