Why did he call Hashem "Malki mi'Kedem"?
Rashi: You are our salvation from of old.
Radak: How did You leave us in Galus so long? You used to be my King, and did for me salvations in the land! Now it is as if You are not my King, for others have their way with me.
Malbim: Before You were my King. Not only You did not return Your hand to Your bosom - You bared Your outstretched arm miraculously!
Why does it say "b'Kerev ha'Aretz"?
Radak: This is like it says about Pharaoh "Teda Ki Ani Hashem b'Kerev ha'Aretz" (Shemos 8:18). Even though I am supreme, I oversee lower beings and do to them as I wish. "B'Kerev" - even in their enemies' land, the enemy cannot save from Me.
Malbim: Miracles that Hashem does via nature and the Ma'arachah, He does them in Shamayim, for He is Elokei ha'Shamayim and conducts the Ma'arachah of Shamayim in a way that Yisrael will be saved naturally. If He does a miracle unlike nature fixed in Shamayim, this is below in the land, even though the prior causes from Shamayim did not agree to it.
