1)
Did David say so when he was still ill?
1.
Radak #1, Malbim: This was after he recovered.
2.
Radak #2: He was still ill; he discusses the future, with Ru'ach ha'Kodesh. Every Choleh who prays via saying this Mizmor may say so, for Hashem will hear his Tefilah if he prays with a broken, crushed heart.
