Why does it say "beha'Shamayim Chasdecha"?
Rashi: Due to these Resha'im, You remove Your Chesed from the lower beings, and raise Your Emunah to Shechakim (Heaven), to remove it from people.
Radak: Your Chesed is Ad (until) Shamayim. This is like "b'Lo Yuchlu Yig'u bi'Levusheihem" (Eichah 4:14), and perhaps also "v'Shilach Es ha'Sa'ir ba'Midbar" (Vayikra 16:22) is Ad ha'Midbar. Your Chesed and Emunah are constant; they keep the species alive.
Malbim: Now is the refutation of Pesha's claim that there is no reward and punishment. As long as Hashem conducts via nature (refer to 36:6:4:2), Resha'im can prosper and Tzadikim can be afflicted, if such is their Mazal. The Torah testifies that nature is drawn after man. Men receive Brachos or curses, based on their deeds. If so, Chesed (miraculous conduct) is also in Shamayim, not only in Shechakim.
Why does it say "beha'Shamayim", and not 'ba'Shamayim'?
Radak: It is proper to have both prefixes, just in most places the Hei is omitted to facilitate [saying the word].
What is so special about Chesed and Emunas Hashem?
Radak: Emunah keeps the species intact. Even if individuals die, the species remains - "Lo Sohu Vera'ah Lasheves Yetzarah" (Yeshayah 45:18); "l'Dor va'Dor Emunasecha Konanta Eretz va'Ta'amod" (Tehilim 119:90). Chesed is preparing sustenance of the world. He summons food for each species without great exertion - "Matzmi'ach Chatzir la'Behemah", "ha'Meshale'ach Mayanim ba'Nechalim" (104:14, 10). The world could not exist with great toil! What is needed most (air) is more available than what is needed less (water, and less than water, food). His Chesed is mentioned regarding the Rasha, for He supplies food even for those who deny Him.
Is there a difference between Shamayim and Shechakim?
Radak: No. Shechakim is Shamayim. Also Emes reaches until there - "Ad Shamayim Chasdecha v'Ad Shechakim Amitecha" (57:11). "Ad Shechakim" teaches from the land until Shamayim - "Ki ch'Govah Shamayim Al ha'Aretz Gavar Chasdo Al Yere'av" (103:11). Another verse says that His Chesed is even higher - "Gadol me'Al Shamayim Chasdecha" (108:5).
Malbim: Yes. Hashem runs His world in two ways. (a) Natural conduct based on laws that never change - day and night, winter and summer, rain and drought 1 . This is fixed in Shamayim, via the motion of the Galgal (sphere on which celestial bodies revolve). This is called Emunah in Tanach; Hashem guards His Emunah and does not change it - "l'Olam Hashem Devarcha Nitzav ba'Shamayim; l'Dor va'Dor Emunasecha" (119:89-90). (b) Hashem changes nature and does miracles according to the current need. This is called Chesed; it is fixed in Shechakim, which is above Shamayim. The Torah testifies that nature is drawn after man. If so, Emunah (fixed conduct) is also in Shechakim, not only in Shamayim.
In verse 7, Malbim says that Hashem sends rain based on people's actions! There he said Matar, which is via Hashgachah. Here he discusses Geshem, which is natural, based on evaporation [and condensation], like he said in Bereishis 2:5.
