Nehemiah 4:16
And it came to pass from that time forth, that the half of my servants wrought in the work, and the other half of them held both the spears, the shields, and the bows, and the habergeons; and the rulers were behind all the house of Judah.
The setting is the rebuilding of Jerusalem's wall when neighboring enemies sought to hinder the work. After the threat against the rebuilding was exposed, half of the servants labored at building while the other half stood armed with spears, shields, bows, and armor. At the same time the rulers stood behind all the house of Judah.
The arrangement joined continued labor with watchful defense in the face of opposition. By this division the work could go forward without ceasing. At the same time the builders were protected from enemy attack.