What does this Mizmor discuss?
Rashi: It discusses the afflictions that come on those who serve Hashem.
Radak, Malbim: It discusses something that confuses people - serenity of Resha'im and evil that befalls Tzadikim in this world. Radak - Asaf, the author, discusses his words, or the words of all the confused. Also Sefer Iyov speaks much about this. Also Nevi'im elaborated about this. Yirmeyah said "Tzadik Atah Hashem Ki Ariv Elecha Ach Mishpatim Adaber Osach Madu'a Derech Resha'im Tzalechah" (Yirmeyah 12:1).
Why did he say "Ach Tov l'Yisrael Elokim"?
Rashi: Even though I scream and am astounded at Yisrael's afflictions, I know that Hashem is good to them, and He brings the evil for their benefit, to merit the world to come.
Radak #1: Even though they are in Galus, Hashem is good to them and guards their good deeds for them. It says "Ach", for I know that whatever happens, He will benefit them.
Radak #2: "Ach" shows the truth of the matter, like "Ach Atzmi u'Vesari Atah" (Bereishis 29:14), "Ach Melech Yisrael Hu" (Melachim I, 22:32) and similar verses.
Malbim: The author shows that he does not ask due to Safek; he knows that Hashem's conduct is good.
Who are "l'Varei Levav"?
Radak #1: They are among other nations. Even though it is bad for them in this world, it will be good for them in the world to come.
Radak #2: They are those of clear hearts in Yisrael. All the more so their deeds are clean!
Malbim: It is one whose heart is clear and strong in Emunah. I am not among them!
