Why does it say "[Imru] Tzadik Ki Tov"? Are there Tzadikim who are not good?!
Radak (11, citing Kidushin 40a): A Tzadik who is good to Hashem and people is a good Tzadik. A Tzadik who is good to Hashem but bad to people is not a good Tzadik.
Radak #1: The verse instructs to tell a Tzadik that he did good. Radak - it does not address any particular person, rather, everyone, like "Re'e Rei'ach Bni" (Bereishis 27:27). Everyone who recognizes that Hashem's Mishpat is Emes should announce that Hashem will pay to every Tzadik according to his virtue, and to every Rasha according to his evil.
Radak #2: When a Tzadik is good, and does not retract from his virtue and do evil, "they will eat the Peros of their ways" - in this world and in the world to come.
Malbim: Tell the Tzadik that virtue is not something needed for another purpose, e.g. to get honor or reward. Rather, it is an end unto itself. One should not seek another good other than it.
What do we learn from "they will eat the Peros of their ways"?
Radak (11, citing Kidushin 40a): Merit has principal and dividends. Sins have principal (for punishment) but not Peros 1 - "Gemul Yadav Ye'aseh Lo" (11).
Sukah 56b: This teaches that it is good for a Tzadik, and good for his neighbor. (Mishmaros Kehunah. Meromei Sadeh, Sefas Emes - the verse discusses one Tzadik 2 , and says "they will eat" (plural).)
Radak: Refer to 3:10:1:3.
Radak #2: The verse teaches that even though sometimes a Rasha has good in this world, in any case his Nefesh will perish, for "Kel Emunah v'Ein Avel" (Devarim 32:4).
Malbim: A Tzadik's deeds are compared to a tree that makes fruits. The fruits of this tree are the reward for his virtue; it is not separate from his deeds themselves.
Kidushin 40a: It says "they will eat the Peros of their ways, and will be satiated from their (evil) counsel" (Mishlei 1:31)! For sins that have Peros (cause others to sin), the punishment has Peros. Radak (11) - sin is barren. It has no Peros, unless it made Peros, e.g. he had Bi'ah with an Ervah, and fathered a Mamzer.
However, it says "the Peros of their ways" (plural)! Perhaps it implies that also his neighbors will be Tzadikim. (PF)
