What is the meaning of "Hiflah"?
Rashi: He divided. Radak - the same applies to "v'Hiflah Hashem Bein Mikneh Yisrael..." (Shemos 9:4). Hashem separated me from Yisrael to be king. This is like "Hivdil Hashem Es Shevet ha'Levi" (Devarim 10:8).
What is "Chasid"?
Rashi: It is one who does good to his colleague beyond the letter of the law. David did so with many people. They did evil to him, and he did good to them. Sha'ul said "you did good to me, and I did evil to you" (Shmuel I, 24:17).
Why does it say "Lo"?
Radak: Hashem gave kingship to me - how do you intend to steal it from me and give it to someone else?!
Malbim: This is one reason why Hashem will answer me - he separated the Chasid (me) with Hashgachah Pratis to clarify his virtue. Also refer to 4:4:4:2.
Why did he say "Hashem Yishma b'Kar'i Elav"?
Radak: Even though now you see me in affliction, know that Hashem will hear my voice and remove me from this affliction.
Malbim: This is the second reason why Hashem will answer me - He always answers when I call to Him.
