What are the implications of "Vekashlu Ish be'Achiv"?
Rashi #1: It means that, in their haste to escape from the enemy, they stumble over each other
Rashi #2: Refer to 26:37:2:2.
And why does the Torah insert the 'Kaf' in the word "ke'Mipnei Cherev"?
Rashi #1, Targum Onkelos and Targum Yonasan: They will flee in terror as if they were being chased by the sword, when in fact, there is nobody running after them.
Rashi #2: Based on the principle 'All of Yisrael are responsible for one another', one man will stumble over another's sins - just as a man stumbles before the sword that is chasing after him.