1)
Why does it say "Lo Sarti mi'Mishpatecha"?
1.
Malbim: Mishpatim are laws of conduct that the intellect knows. Sometimes a person thinks that he can judge them differently via his intellect. Even so, I did not veer from Your Mishpatim. Who will go against (deviate from) Hashem's Chachmah?!
2)
What is the meaning of "Horesani"?
1.
Radak #1: You showed them to me from the way of intellect. Therefore, they were fixed in my heart and desire, and I did not veer from them.
2.
Radak #2: You helped me to guard them. You opened their path in front of me.
