What is the meaning of "li'F'ulas Adam bi'Dvar Sefasecha"?
Rashi #1: From then (when I asked to be tested) and onwards, for every act of man that I came to do, I guarded due to the word of Your lips.
Rashi #2: One's deeds must be according to the decree of Your lips. You said, "Lo Sin'af."
Radak: In what You commanded and forbade, I contemplate people's actions, and stop them from sinning.
Malbim: Just like I guarded from sin in thought, also in deed. If You test people's actions, what You warned not to do, You will find that I guarded from Isur, from going in the way of the unruly, who breach fences.
What is the meaning of "Shamarti Archos Paritz"?
Rashi: I guarded from going in the ways of the cruel, even though I did improperly with Your good [that You gave to me].
Radak #1: I did like the Rasha and cruel.
Radak #2: I stopped people from going in the ways of the cruel. This is like "Lishmor Es Derech Etz ha'Chayim" (Bereishis 3:24) - to stop people from going there, and "Shomer ha'Pardes" (Nechemyah 2:8).
