When will they leave the ambush [to go to the city]?
Malbim: When they see the sign of the spear.
What is ha'Orev?
Radak: It is a noun (the ambush), like ha'Me'arev.
Malbim: It is the place of the ambush.
What is the meaning of "v'Horashtem"?
Rashi: You will cut them off.
Radak: You will expel them and finish them off.