What is the meaning of "Mi Chacham v'Yishmar Eleh"?
Radak: One who is a Chacham will guard from the matters said in this Mizmor. He will guard them in his heart and recognize that everything is in Hashem's hand; He raises, lowers, makes rich, impoverishes, strikes and heals.
Malbim: A Chacham who accepted the laws of Chachmah, he will guard this, and bring from this an attestation of Hashem's Hashgachah.
Why does it say "va'Yisbonenu Chasdei Hashem"?
Radak: They will contemplate Hashem's Chasadim with those who do His will. Even though in this world a person sees serenity for Resha'im and evil for Tzadikim, if he contemplates actions in the world, he will see that most [of them show] that He is "Kel Emunah v'Ein Avel" (Devarim 32:4), "v'Lases l'Ish ki'Drachav ki'Fri Ma'alalav" (Yirmeyah 17:10). The minority that he sees that is not in order, he will say that Hashem knows why; we do not know. He will attribute the ignorance to himself, and not attribute injustice to Hashem.
Malbim: They will contemplate that the world is not Hefker, rather, everything is with Hashem's Chesed and Hashgachah.
