Why did David compose this Mizmor?
Malbim: This is connected to the previous Mizmor; refer to 32:1:1:1. Hashem runs His world in two ways. (a) Natural conduct based on laws that do not change. (b) Conduct based on Hashgachah, based on people's actions.
Why does it say "Ranenu
Radak #1: This is like la'Shem. Similarly, "v'Shilach Es ha'Sa'ir ba'Midbar" (Vayikra 16:22) is like la'Midbar.
Radak #2: Your singing and praise should be in Hashem, and not in anything else.
What is the grammatical form of "Navah"?
Radak #1: The Aleph is the first letter of the root. It is silent, and also elsewhere, e.g. "Navu Lechayayich ba'Torim" (Shir ha'Shirim 1:10). The only exception is "l'Veischa Na'avah Kodesh" (below, 93:5). The Nun is due to the conjugation.
Radak #2: Perhaps the Nun is from the root; the root is Na'eh. Chachamim used this root, e.g. Lulav Na'eh (Shabbos 133b).
Is praise proper only for "Yesharim"?
Radak: It is most proper for them for they understand Hashem's actions and His Chesed with His creations.
Malbim: Yes. Yesharim is a higher level than Tzadikim. Their heart and intellect are straight, without any Safek or veering at all from Hashem's ways. Tzadikim do proper deeds, but they have inner wars - intellectual wars about Emunah and mindsets, and wars of their Yetzer ha'Ra regarding deeds. They should be happy in their hearts; Yesharim should sing. The Mizmor says that Tzadikim will come to the level of Yesharim, who have no Safek. "Navah Sehilah" means that they will tell Hashem's praise, and also that they are worthy of praise for their straight intellect.
