What is the meaning of "Yashur"?
Rashi: It is waiting in ambush. The same applies to "Lema'an Shorerai" (Tehilim 5:9). This is related to "Ashurenu v'Lo Karov 1 " (Bamidbar 24:17). Radak - he looks [for people coming his way from whom he can steal].
That verse refers to seeing! Perhaps Rashi means like Radak - he looks to see whom he can ambush. Radak (Tehilim 5:9) - Shorerai look for evil to come on me. (PF)
What is "k'Shach Yekushim"?
Rashi: Like the trap bites (snaps shut on the deer's leg), and it is caught.
Radak: Like one who sets traps to catch birds, they look to ambush and steal from people. Yekushim is a noun, like Mukashim (traps).
Radak citing Targum Yonasan: They are liable for guile; they spill innocent blood.
Malbim: [When a bird is caught, the trapper resets the trap only after] the caught bird [despairs,] calms down and is quiet. Before this, other birds would sense that other birds were caught there, and would beware! So these Resha'im, after killing someone, they wait until the matter quiets down, and then they trap others.
Why does the Navi mention specifically lying in ambush?
Malbim: The Aveiros of theft and murder are against natural laws and endurance of the world. Therefore, nature itself punishes the sinners. We find that Hevel's blood "is crying to Me from the ground" (and Kayin was cursed from the ground - Bereishis 4:10-12).
What is the grammatical form of "k'Shach"?
Radak #1: It is Makor (like an infinitive), like k'Hani'ach.
Radak #2: It is a To'ar (type of person) like Meni'ach. It is related to "va'Chamas ha'Melech Shachachah" (Esther 7:10). Shach is Po'el Yotzei (it acts on others); Shachachah is Po'el Omed (the action applies only to the subject).
What is the meaning of "Hitzivu Mashchis"?
Rashi: They stationed marauding troops around a besieged city. This is like "Matzav Pelishtim" (Shmuel I, 13:23).
