Why does it say "v'Ra'u Bechorei Dalim"?
Rashi: They will graze in the days of Sarim of Yisrael, who are now poor due to you. Bechorei is an expression of officers, like "Gam Ani Bechor Etnehu" (Tehilim 89:28).
Rashi: Until now, Yisrael had Bechorah and a great portion in poverty. Now they will graze without fear of their enemies, and they will lie down securely. The verse compares them to flock that graze in the Midbar without fear. While their enemies ruled over them, they did not leave their fortified cities, and they were hungry. Now they will leave to [go to] any place without fear, and they will be satiated from the good of the nations.
Malbim: The serenity of Yisrael is compared to animals grazing in a grassy place. The mature animals graze, and the small ones lie by them.
Why does it mention "Dalim" and "Evyonim"?
Malbim: Evyonim are worse than Dalim.
Who are "Sharshech"?
Radak: It is those who will gather to the fortified cities. They will die of hunger [Malbim - during the siege], and Yisrael will graze.
Malbim: The Giborim and great people.
Who are "She'erisech"?
Radak: It is those who will survive the hunger (Malbim - siege).
Malbim (31): Sancheriv conquered Pelishtim three years before he fell in Eretz Yehudah. "She'erisech" are those whom he did not kill.
Who will kill them?
Radak: Chizkiyah. Hashem says "v'Hamati",, for Chizkiyah's act is attributed to Him, for it is with His help.
Malbim: The enemy that conquers them.
