What is the meaning of "Kol Mishpatav l'Negdi"?
Rashi: I always put them in front of my eyes.
Radak: I never forgot them. 1
Above (verse 22), Radak said 'if I left His path, it was Shogeg'! We can say that he never forgot the Halachah, only the case (that this item is Asur, or Tamei... - PF).
Why did he distinguish Mishpat and Chok?
Malbim: Mishpat is what intellect obligates. Chok is what intellect does not understand. Negdo is opposite the person, outside of him. "Lo Asir Mini" shows that it clings to him, and he does not cast it off. The Mishpatim are Negdi - I do not keep them because my intellect says so, rather, because Hashem commanded them. It is as if they are opposite me, not in me; I accept them from Hashem, like matters far from intellect. I view the Chukim as if they are in my intellect, and not outside of me - "Natisi Libi La'asos Chukecha" (Tehilim 119:112). Amidst his Eumnah in Hashem, his heart is drawn to them like Mitzvos that intellect obligates, to the point that I will not veer them from me; they are rooted in my heart and Nefesh.
Why did he say "v'Chukosav Lo Asir Mini"?
Radak: I did not turn my heart to idle matters. I was always careful from every sin, with all my strength.
Radak (Shmuel II, 22:23): [I will not veer] from every Mitzvah and statute.
