Why does it say that Shamayim will thank for His wonders?
Rashi: If He would guard His promise [then Shamayim will thank].
Radak: If I thank for Your Chesed and Emunah, I see that Shamayim thanks for Your wonders - "ha'Shamayim Mesaperim Kevod Kel" (19:2). The constant rotation of the spheres is wondrous; it shows that there is One who moves them. They will admit that all their strength is from You.
Malbim: Every day, existence testifies to Hashem's Chesed and Emunah, both regarding natural and miraculous conduct. It also testifies to His establishment of Malchus Beis David. Even though miraculous conduct is via angels above Kisei ha'Kavod (in Shamayim) - "Serafim Omedim mi'Ma'al Lo" (Yeshayah 6:2), also Shamayim admits to it. Also Shamayim alters fixed [natural] laws to conform with wondrous conduct.
What is "Emunasecha"?
Rashi: Fulfillment of Your words.
Radak: It is their continued existence. The angels exist forever, for they are not physical, and they make Shamayim, which is physical, endure.
What is "Kahal Kedoshim"?
Radak: It is the angels. Through their existence, the spheres endure.
Malbim: It is the angels. Miraculous conduct is via them.
