What is the significance of "[Yode'a Tzadik] Din Dalim"?
Shabbos 155b: Hashem knows that dogs do not find food in abundance, therefore He caused that its food stays in its innards for three days.
Rashi: Poor people's afflictions and what they need - he puts his heart to them.
Malbim: Tzadik is one who does acts of Tzedek. Mishpat is a clear law. Din is claims in a matter that is not clear. Even so, the Tzadik knows [the Oni's] Din clearly. Via engaging in an act of Tzedek, he recognizes with whom is Tzedek.
Why does a Rasha not understand Da'as?
Malbim: Not only does he not know Din - he does not understand even Da'as (clarified Mishpat). Amidst his evil, his path is the opposite of Tzedek and Mishpat, therefore he does not understand known Mishpat.
