"The Spirit of the Lord GOD is upon me, because the LORD has anointed me to bring good news to the afflicted; he has sent me to bind up the brokenhearted, to proclaim liberty to captives and freedom to prisoners..."
Then he reminds Israel of their hopeful redemption as a nation of priests. He ends with praise. And why rejoice? I will let the text speak for itself:
"I will rejoice greatly in the LORD, my soul will exult in my God; for He has clothed me with garments of salvation, He has wrapped me with a robe of righteousness, bridegroom as decks himself with a a garland, and as a bride adorns herself with her jewels. For as the earth brings forth its sprouts, and as a garden causes the things own in it to spring up, so the LORD GOD will cause righteousness and praise to spring up before all the nations."
- Isaiah 63:1; 63:10f