42:6-7  It is G-d Who has called the Mashiach to his great mission of returning the Jewish people to the Covenant.  To this end, G-d will strengthen him, "hold his hand," and watch over him from all harm.

But his mission is not just to the Jewish people, but also to all the nations - for them, too, will he serve as a light.  He will enlighten, "open blind eyes," those who previously could not see G-d's truth.  But the Jewish people were also "blind" throughout the exile and G-d will release them from their spiritual "prisons."