In 51:9-16 we see Jehovah's arm for Israel. As 53:1-2 indicates, Jehovah's arm is Christ the Servant of Jehovah. Hence, Jehovah's arm for Israel is actually Christ for Israel. In 51:9a there is the prayer that Jehovah's arm would arise and put on strength. Because of Jehovah's arm, the ransomed of Israel will return and come to Zion with a ringing shout, and eternal joy will be upon their heads. They will lay hold on gladness and joy, and sorrow and sighing will flee away (v. 11). Furthermore, the one who is bowed down (that is, in bonds, denoting the captives) will soon be released and will not die in the pit (that is, in prison), nor will his bread be lacking (while the released captives will be on their way of returning—vv. 14-16).
Isaiah 51:17-23 is concerned with Jehovah's encouragement to Jerusalem. Verses 17 through 20 speak of Jehovah's wrath and of His rebuke to her in the past. According to verses 21 through 23, Jehovah now is pleading for her.
Isaiah 52:1-6 tells us of Jehovah's encouragement to Zion.
In 52:7-10 we have Jehovah's good news for Zion and Jerusalem. Verses 7 and 8 say, "How beautiful on the mountains/Are the feet of him who brings good news,/Of him who announces peace, who brings news of good things, /Who announces salvation;/Of him who says to Zion, Your God reigns!/The voice of your watchmen! They lift up their voice;/They give a ringing shout together;/For they will see with their very own eyes/When Jehovah restores Zion." The first part of verse 7 is quoted by Paul in Romans 10:15. Isaiah 52:9 and 10 go on to say, "Break forth, give a ringing shout together,/You wasted places of Jerusalem,/For Jehovah has comforted His people,/He has redeemed Jerusalem./Jehovah has bared His holy arm [Christ, the Servant of Jehovah]/In the sight of all the nations,/And all the ends of the earth will see/The salvation of our God."