1)
Why did he say "Ki Hecherashti"?
1.
Rashi: When I was silent from confessing my sin in front of You "[my bones wore out."] Malbim - this shows how great is the sin of covering sin! 1
2.
Radak: "Ki" is like Ka'asher, like "Ki Solid Banim" (Devarim 4:25). When I was silent and thought about sin, "my bones wore out" from great worry.
2)
Why did his bones wear out?
1.
Rashi: It was amidst sighing and worry [over my sin].
3)
Why did David roar the entire day?
1.
Rashi: It was due to worry of punishments.
2.
Malbim: Your hand (afflictions) was heavy on me day and night (verse 4).
