Nehemiah 4:22

Likewise at the same time said I unto the people
That were at work upon the wall:

let everyone with his servant lodge within Jerusalem;
every builder had a servant, or a lad, as the word signifies, to wait upon him, to bring mortar or stone, or what he wanted; and some of these builders, with their lads, came out of the country towns and villages in the morning, and returned at night; now Nehemiah proposed, for the safety of the city and its walls, that for the present they would lodge in Jerusalem:

that in the night they may be a guard unto us, and labour on the day;
might help to protect them in the night, should they be surprised with the enemy, and be ready for their work in the daytime.