G-d says that He can take captives from the mightiest rulers and He will rescue us. Those who oppress Israel will be so distressed that they will become physically ill. Everyone will know that it is G-d Who has saved Israel.
G-d says that, despite their sins, He has not "divorced" the Jewish people. (This seems to contradict Jeremiah 3:8, which says that He did. However, Jeremiah was prophesying to the Ten Tribes of the Northern Kingdom - the now "lost" Tribes - while Isaiah was speaking to the kingdom of Judah.) Why does G-d call for us to return, but no one answers? Is the exile so long that you think He is unable to save you? Whenever He wishes, G-d could dry up the sea, as He did the Red Sea when the Jews left Egypt, or stop a river from flowing, as He did the Jordan when the Jews entered Israel. He dresses the Heavens with darkness and covers them with sackcloth.
G-d gave Isaiah the ability to teach the weary the word of G-d. G-d rouses Isaiah every day, energizing him to hear His teachings. G-d appointed Isaiah His prophet and Isaiah accepted the job without any hesitation, unlike many other prophets. He did his appointed task, despite the insults and abuse his detractors would heap upon him. G-d gave him the strength to carry on with his task.
Soon, Isaiah says, he will be vindicated - let those who wish to debate him step forward! G-d will help him and his opponents will wear out like moth-eaten clothes. Who fears G-d and heeds the words of His prophets in darkness? Let such a person rely on G-d! But those who do not listen ignite the fire of G-d's anger and are thereby burned accordingly. This is payback and these people will have no strength before their enemies.
Isaiah tells the righteous to listen to him: Look at the rock from which you were cut and the hole from which you were dug - referring to Abraham and Sarah. Abraham was a lone person when G-d called him and G-d blessed him to become multitudes. G-d will console Israel, turning wasteland into gardens. Rejoicing will be found in the land. Words of Torah will shine forth and G-d's judgment will be a light to nations; they will have rest from war.
Excerpted from The OU's Nach Yomi