When did David's sighing begin?
Radak: It was from when he killed Galyus. The women sang "v'David b'Rivevosav", "vi'Yhi Sha'ul Oyen Es David meha'Yom ha'Hu va'Hal'ah" (Shmuel I, 18:7, 9). David's agony began then, for he was a step from death.
What weakened him?
Radak: His sighing, amidst fear of Sha'ul. Sighing breaks a person's body (Brachos 58b). This was "ba'Avoni" - due to my sins.
Malbim: Due to my sins, my afflicters reviled me. They say that due to my sin, my strength weakened and my bones rotted.
What is the meaning of "Asheshu"?
Rashi: It is an expression of decay 1 , like "Ash Yochlem" (Yeshayah 50:9).
In verse 10, Rashi explained that it is an expression of weakening. (PF)
Why did he mention the bones decaying?
Radak: They are a person's strength and the foundation of the body.
