What is the answer "mi'Lifnei Adon..."?
Radak (5, 7): This is like a slave who is zealous and shakes due to [fear of] his master. "Aretz" includes the sea, Yarden, mountains and hills.
Malbim: The Master Himself descended in His honor to oversee - therefore the land should shake.
What is the meaning of "Chuli Aretz"?
Rashi: He makes the land. The Yud is extra, like Magbihi, Mashpili, ha'Hofchi (113:5-6, 114:8).
Radak: The land says, it is the One (Master in front of whom I shake, fear, dance and flee. Chuli is Makor (like an infinitive); the Yud is a pronoun (He makes me shake.
Malbim: Refer to 114:7:1:3.
Why does it say "Eloka Yakov"?
Radak: He acquired him from Beis Avadim with His strength. He is Master over everything and does like His will. If He wants Bnei Yakov to pass through the sea or Yarden, they should flee and split the water in front of Him, for He is the Master!
Malbim: The Master revealed Himself because He is "Eloka Yakov" - He has a connection with Am Yisrael.
