According to the book of Nehemiah, Nehemiah told the people to keep the city gates closed and only open them when the sun is hot. He asked them to make sure people were watching over the city to keep everyone safe, with each person looking after their own area.
Nehemiah 7:3: And I said unto them, Let not the gates of Jerusalem be opened until the sun be hot; and while they stand by, let them shut the doors, and bar [them]: and appoint watches of the inhabitants of Jerusalem, every one in his watch, and every one [to be] over against his house.
This verse suggests that unless the Lord watches over the city, the watchmen stay awake in vain, which contrasts with Nehemiah 7:3's directive for human vigilance.
Psalm 127:1: [A Song of degrees for Solomon.] Except the LORD build the house, they labour in vain that build it: except the LORD keep the city, the watchman waketh [but] in vain. [for...: or, of Solomon] [that...: Heb. that are builders of it in it]