What is the meaning of "va'Ani ba'Chalosam Levushi Sak
Radak: If one of them was ill, I was pained and worried. I wore sackcloth, fasted and prayed that Hashem heal him. Mesilas Yesharim (Perek 19) - the more Chesed that one does, he will receive more. David prayed based on this, that he strove to help even his haters.
Malbim: When they were ill, I was so pained that I was bedridden. They rejoiced over this, and hoped for the day of my death. I did all that I can for them - I wore sackcloth, fasted and prayed for them (refer to 35:13:3:3).
Why is there a Patach under the Veis in "va'Tzom"?
Radak: It is the known fast, which relatives of the Choleh fast. I fasted as if it was my brother or relative.
What is the meaning of "u'Sefilasi Al Cheiki Sashuv"?
Rashi: If they will say that I afflicted myself only for their evil, that their illness should get worse, what I prayed about them should come upon me!
Radak: The good that I prayed for them, should come upon me! Do not think that outwardly I showed that I am worried for them, but covertly I prayed oppositely, for their evil.
Malbim: My prayer for them was with intent El Cheiki, i.e. in the heart. It was not to show others that I strive for them. It was not only one Tefilah - it returned (was repeated) time after time.
