Why does it say "Al Telech b'Derech Itam"?
R. Yonah: This refers to the path that sinners counsel you to go with them, to ambush and take booty. There is Sheva under the Beis, and not a Patach, for it did not need to warn not to go to ambush (their known path). Rather, do not join with them, for you know that they are sinners. Yir'as Hashem mandates separating from their company. There is a big punishment [for joining to them] - "Im Shonim Al Tis'arev; Ki Pis'om Yakum Eidam u'Fid Sheneihem Mi Yode'a" (24:21-22).
Malbim: Refer to 1:15:2:2.
What is the meaning of "Mena Raglecha mi'Nesivasam"?
R. Yonah: Also when they go to their affairs and work, do not join with them. They are sinners; perhaps they will have opportunity to steal, harm or do another sin, and entice you to sin with them. You will be punished if you will not protest against them. Also, one who join to a Rasha and goes in his steps is punished, for his steps are destined to sin. A sinner always looks to do evil and damage. One who joins with those who transgress is like one who transgresses (Sanhedrin 9a). "K'Hischabercha Im Achazyah Paratz Hashem Es Ma'asecha" (Divrei ha'Yamim II, 20:37). The coming verse proves so, and the repetition [within our verse].
Malbim: Derech is the great path fixed for the Rabim. Nesivos are individual paths. Not only should you not go on their big path for everyone - also do not go an individual's path (if he is a Rasha). Even after he went on the path, do not go on his path - they will kill also you!