Why will people say "Ach Pri la'Tzadik"?
Rashi: They will say that surely there are Peros and reward for deeds of Tzadikim; Hashem took vengeance for them!
Malbim: Vengeance (refer to 58:11:2:1) will say so to the Tzadik and people standing there. It says 'Adam - see the fruit of the Tzadik. He has a good reward!'
Why will they say "Yesh Elokim Shoftim ba'Aretz"?
Rashi: There is a judge judging Resha'im in the land.
Radak #1: Before, they thought that Hashem does not see and does not know [Resha'im's deeds]. Then, all will know that Hashem oversees people's matters and judges according to their deeds. It says "Shoftim" (plural) for honor, like "Elokim Kedoshim Hu" (Yehoshua 24:19).
Radak #2: This refers to angels; they are Hashem's messengers to judge in the land.
