What is the meaning of "Irchu"?
Radak: Arrange war.
What is the meaning of "Yedu Eleha"?
Rashi: Throw rocks at it. The same applies to "va'Yadu Even Bi" (Eichah 3:53).
Radak: Throw arrows or rocks at it. The Kaved form (Pi'el, with a Dagesh) of this is "Leyados Es Karnos ha'Goyim" (Zecharyah 2:4).
Malbim: Do not shoot the arrows via the bow. Rather, throw them by hand. Also by hand, they will stroke the target!
What is the meaning of "Al Tachmelu El Chetz"?
Radak 1 , Malbim: Do not be concerned for your arrows, and say 'perhaps we will shoot, and not strike a person.' [Do not say so; the arrows] will not return empty, like it says above (verse 9). Every arrow that you shoot will kill someone, for "la'Shem Chata'ah."
Radak: El is like Al; there are many verses like this.
