watch and ward
Noun
Meaning
(law) The charge or care of certain officers to keep a watch by night and a guard by day in towns, cities, and other districts, for the preservation of the public peace.
(by extension) Uninterrupted vigilance.
Source: en.wiktionary.orgSynonyms
Examples
We are not here today to bow before the representation of a fierce warlike god, filled with wrath and vengeance, but we joyously contemplate instead our own deity keeping watch and ward before the open gates of America and greater than all that have been celebrated in ancient song.
Every citizen of the republic ought to consider himself an unofficial policeman, and keep unsalaried watch and ward over the laws and their execution.