What is "Samar"?
Rashi: This is like "Tesamer Sa'aras Roshi" (Iyov 4:15), like one whose hairs stand [Radak - like Masmerim (nails), amidst fear].
Why does he fear "Mishpatecha"?
Rashi: He fears the punishments of Your decrees.
Radak: I fear lest You judge me according to my deeds. Therefore I am careful not to transgress Your Mitzvos and Mishpatim, for I know that You see me and know my deeds 1 . This is unlike Resha'im, who do not fear You; they err to say that You do not see them.
Malbim: Since You eradicate Resha'im, fear of You falls on all flesh 2 .
Radak: "Es Hashem Elokecha Tira" (Devarim 10:20) - refrain from sin due to fear of Hashem, who commanded about them, and not for another reason.
What is his source? The verse says "my flesh", and "I fear"! (PF)