“After him Nehemiah (III) son of Azbuk, ruler of half the district of Beth-zur, repaired the wall to a point opposite the sepulchers of David, and to the artificial pool and the house of the guards.” Nehemiah 3:16
The third chapter of the book of Nehemiah describes how he and the remnant in Jerusalem worked to rebuild the walls around the city. What came to mind for me was that through their disobedience the children of Israel had torn down the walls God provided protecting them. Literally their enemies had torn down the physical walls around Jerusalem, but we need to see this in a spiritual mindset. The book of Ezra, which by the way did not have a 3:16 verse, and the book of Nehemiah tell about the return of the remnant, taken into captivity to Babylon, to rebuild the walls around the city. They spiritually return to a right relationship with God as well, and He starts rebuilding the walls around their hearts to protect them from evil.
When we sin our walls of protection that God provides will fall and God will allow us to be taken captive by the world. When we return to Him in repentance He will help us rebuild our walls as well.