Why does it say "Al Mah Tuku"?
Rashi: If one was lashed and returned to his sin, his friend will rebuke him, and say 'you were lashed for this. Do you not heed to say, I was lashed for this - I will not return to do it again!'? Also here, why were you stricken? "Od Tosifu Sarah" to veer from Hashem. Already, "every head is ill" - why do you not understand?!
Radak #1: Do you not put to heart why you are stricken?!
Radak #2, Malbim: What benefit was there to strike you? You were not chastised via this. You continue to sin more.
What is the meaning of "Od Tosifu Sarah"?
Radak: You do not think that Kel strikes you for your sins, rather, you go by chance, and you say that evil chanced upon you; it is not a punishment for your sins. "Sarah" is an adjective - a deviant, crooked way.
Why does it say "Kol Rosh la'Chali"?
Radak: Do not think that if Hashem strikes you, and you say that by chance, evil illness fell on all of you. This is a punishment for your sins, for every head is summonsed for illness, and "every heart [to be] faint." Also Moshe said "Yakecha Hashem b'Shiga'on uv'Ivaron uv'Simhon Levav" (Devarim 28:28).
Malbim: This shows that you will not repent. Every head is ill, yet you did not begin to engage in a cure! The Klal of the nation is depicted as an individual stricken with pain from head to toe. The general illness is of the head, for all sensation comes from the brain and all the limbs feel its pain. A lower level illness is of the heart, which gives life to all the limbs via blood circulation. When the heart is ill, the limbs feel its pain more than the head's pain, even though the illness is smaller. This is a metaphor; it is explained below (refer to 1:7:1:1).
