1)
When will they leave the ambush [to go to the city]?
1.
Malbim: When they see the sign of the spear.
2)
What is ha'Orev?
1.
Radak: It is a noun (the ambush), like ha'Me'arev.
2.
Malbim: It is the place of the ambush.
3)
What is the meaning of "v'Horashtem"?
1.
Rashi: You will cut them off.
2.
Radak: You will expel them and finish them off.