Who are "Sarim"?
Radak: They are officers and nobles who do not desire Torah.
What is the meaning of "Bi Nidbaru"?
Rashi: Even though Nochri kings mock me, that I engage in Torah [I speak of Your Chukim].
Radak: They sit in corners and speak condescendingly about me. This is like "va'Tdaber Miryam v'Aharon b'Moshe" (Bamidbar 12:1). The Nif'al teaches that they constantly speak [about me].
Why does it say "Avdecha Yasi'ach b'Chukecha"?
Radak: I am not concerned for what they say about me, for I am Avdecha; I do Your Mitzvos like a slave does his master's command.
Ma'alos ha'Torah: Refer to 119:15:1:2.
Malbim: Even though officers say that there is no reason for Chukim, and Nochrim ask the reason, I am Your Eved. A slave does his master's decrees without concern for disgrace or any matter.