The third return from exile occurs thirteen years after Ezra the priest comes back. While Ezra was mostly concerned with the purity of the community, Nehemiah is focused on rebuilding the walls of Jerusalem. The walls matter not only because they protect the city, but they also define it and allow God’s people to separate from the Gentile peoples who worship idols.
Pay attention to the big celebration in chapter 8. This is really the high point of the book of Ezra-Nehemiah. Notice how the center of activity is the Law of Moses. The people realize that if they are going to succeed as a people, they have to understand what God requires of them.
Unfortunately, the book ends on a sad note (ch. 13), as it shows that the people are still failing to obey. This sets the stage for all the years that follow (which are not recorded in the Bible), in which the Jews struggle to keep God’s law. By the time that Jesus comes, most people are not obedient, as is clear from the call of John the Baptist that they need to repent.