good work. This work was "good" because it was "prepared" by God. See Ephesians 2:10.
Related Commentaries of Nehemiah 2:18
Nehemiah 2:18
18 Then I told them of the hand of my God which was good upon me; as also the king's words that he had spoken unto me. And they said, Let us rise up and build. So they strengthened their hands for this good work.