Why does it say "Ru'ach Hashem Elokim Alai"?
Radak: The good tidings that he said and will say, it is Ru'ach Nevu'ah from Hashem that rested on him. Hashem sent him to herald for Yisrael who will later be in Galus a long time. They will find consolation written, and not despair of redemption.
Why does it say "Ya'an"?
Radak: This means Ba'avur (in order that). It is possible that Ru'ach Nevu'ah would dwell on him, and he is not a Shali'ach to tell others. He explains that his Ru'ach Nevu'ah was in order to tell others.
How did Hashem anoint Yeshayah?
Rashi: This Meshichah is an expression of authority and grandeur.
Radak: He aggrandized him, and appointed him to be a Shali'ach for these consolations. This is like "u'Mashachta Es Chaza'el", "Timshach l'Navi Tachtecha" (Melachim I, 19:15-16) "Al Tig'u bi'Mshichai" (Tehilim 105:15). Because kings are appointed via anointing, also other appointments are called Meshichah, even though they are not anointed.
Who are "Anavim" and "Nishberei Lev"?
Radak: They are Bnei Galus, who suffer the Galus l'Shem Hashem. If they wanted to depart from His unity and His Torah, they would be like one of the nations in their Reshus 1 .
Malbim: Anavim are people who do not complain. They anticipate salvation. No special Shelichus is needed to rebuke them; I merely herald for them. Nishberei Lev anticipate salvation, but their heart is broken due to the present. I was sent to bandage their hearts, lest they despair.
I.e. like other nations under the rule of Yisrael's captors; they would not be persecuted. (PF)
How will he call freedom for the captives?
Rashi: He will herald the Ge'ulah to them. Malbim - this is for those exiled among Nochrim; he will herald Ge'ulah. For those who are merely captive, he will call them to be freed. For those who are fettered, he will call to release them.
What is the meaning of "Pekach Ko'ach"?
Rashi: Open their captivity, and release them. Radak #1 - even though they are two words, they are like one word.
Radak #2: It is like two separate words. He calls to the incarcerated Pekach - they will be released from their fetters, and Ko'ach - be taken from Galus.
Radak citing his father: The incarceration is called Ko'ach, for they are Nilkachim and incarcerated in it. It is as if it says open your prison and the prisoners will leave.
Radak citing Targum Yonasan: The incarcerated, they will be revealed to light.
