This Mizmor is according to the Aleph-Beis, with a few exceptions. Why does this verse not begin with Beis?
Radak (1) #1: Based on Ru'ach ha'Kodesh, David sometimes deviated. Also there is no [verse beginning with] Vov or Kuf, and two verses begin with Reish.
Radak (1) #2: Beis is in "Bach", which is Samuch to Elokai. Some say that "v'Lamedeni" (in the middle of verse 5) is like a verse beginning with Vov.
Why did he say "Al Evoshah"?
Radak: If You would not give to me my request, I would be ashamed of my trust [in You] - "Boshu Ki Vatach" (Iyov 6:20), "Becha Vatchu v'Lo Voshu" (above, 22:6). If You will give to me my request that I trusted that You will give it to me, I will not be ashamed.
Malbim: In physical matters, I trust in You for everything. Therefore I request and I am not embarrassed. It is as if the purpose of the request is only to reach the Emunah, that I will not be embarrassed for trusting in Hashem.
Why is he concerned lest his enemies rejoice over his [shame]?
Malbim: It would be Chilul Hashem.
