1)
What is the meaning of "Yaguru Alai"?
1.
Rashi: They gather 1 in my house to guard me.
2.
Radak: They gather against me. This is like "Yaguru Yitzponu" (57:7).
1
This is based on old texts of Rashi that say 'Likanes'.
2)
Why did he say "Lo Pish'i"?
1.
Radak: They do not ambush me due to sin. I did not sin against them! Malbim - rather, it is because they are "Azim" (brazen).
3)
Why did he say "Hashem"?
1.
Radak: He calls to Hashem.