It already said that what they gave to Egypt was for naught. Why does it add "Hevel va'Rik Ya'azoru"?
Malbim: Not only can they not help now - they never helped a nation that trusted in them. Hevel is something without substance. Rik is a shell without content. Even if Egypt wants to help, their help is Hevel and very weak. However, even their weak help is merely promises; they do not do. It is only a shell and externality. Inside it is Rik; they do not want to give the weak help that they could.
What does "la'Zos" refer to?
Rashi: It is Egypt.
Radak: It is Yerushalayim.
What is the meaning of "Rahav Hem Shaves"?
Rashi #1: They are idle [from work] and are haughty without reason.
Rashi #2: It is proper for their haughtiness to be Shoves (cease).
Radak: Their strength is dwelling in Yerushalayim. They could not request help from Egypt, for it will not help them 1 . Rahav is strength, like "v'Rahbam Amal va'Aven" (Tehilim 90:10).
Malbim: Rahav is haughtiness above their strength (false pride; really, they are weak). Shaves is that their help is hollow; they are idle from any work or Avodah.
They did request! Perhaps Radak means that they could not request help in place of dwelling in Yerushalayim, for it would not help them. (PF)
