Why does it say "Chilu mi'Lefanav"?
'Rashi': When a king sees that people fear him, he instills more fear on them, and they worry more lest he destroy all their houses. Hashem does not do so. When the world fears Him, then it is established and it will not falter. He takes vengeance, and the straight endure, and the land endures and does not falter. Therefore, the entire land should fear Him and not worry; He will only come to fix the land to settle it. When people do not fear Him and sin, he overturns them and destroys them!
Radak (Tehilim 96:9): You did not fear Him until now. When you see His wonders, fear Him!
Malbim (Tehilim 96:9): Realize that He lowers Himself to see in Shamayim and Aretz. He can destroy nature and conduct via Hashgachah. (Therefore, fear Him!)
What is the meaning of "Af Tikon Tevel Bal Timot"?
'Rashi': Refer to 16:30:1:1.
Radak (Tehilim 96:10): The entire world will be b'Shalom. "Lo Yisa Goy El Goy Cherev Lo Yilmedu Od Milchamah" (Yeshayah 2:4).
Malbim (Tehilim 96:10): Even though Hashem established fixed natural laws that never falter, with His Chachmah He arranged that nature will agree with Hashgachah according to deeds. Even though the land is established on natural laws, He judges nations for reward or punishment. Natural laws are drawn after people's actions - "v'Hayah Im Shamo'a Tishme'u El Mitzvosai v'Nasati Matar Artzechem" (Devarim 11:14), "Pen Yifteh Levavchem...; v'Atzar Es ha'Shamayim" (ibid., 16-17).
