What is "Haveru"?
Rashi, Targum Yonasan: It is an expression of cleaning. Radak - the root is Barar, like "l'Chetz Barur" (Yeshayah 49:2).
Radak citing his father: It should say He'avru, like "Ever ka'Yonah" (Tehilim 55:7), "Erech ha'Ever" (Yechezkel 17:3), i.e. feathers. Put feathers in the arrows to straighten them 1 .
Malbim: The verse tells the arrows to lift [their] wings and fly by themselves to fill the quivers.
Perhaps feathers cause them to fly straighter. (PF)
What are "ha'Shelatim"?
Rashi: They are quivers in which arrows are held.
Radak: They are shields, like "Kol Shiltei ha'Giborim" (Shir ha'Shirim 4:4).
How did Hashem arouse the kings of Madai?
Malbim: He put in their hearts to destroy Bavel, to take Hashem vengeance. They knew this through Daniel's interpretation [of the vision of the hand that wrote].