keep watch on

keep watch on someone or something

to monitor someone or something. Keep watch on the lady in the big coat. She may be a shoplifter. Try to keep watch on the committee's work.
See also: keep, watch
References in classic literature ?
121-139) But after earth had covered this generation -- they are called pure spirits dwelling on the earth, and are kindly, delivering from harm, and guardians of mortal men; for they roam everywhere over the earth, clothed in mist and keep watch on judgements and cruel deeds, givers of wealth; for this royal right also they received; -- then they who dwell on Olympus made a second generation which was of silver and less noble by far.
For upon the bounteous earth Zeus has thrice ten thousand spirits, watchers of mortal men, and these keep watch on judgements and deeds of wrong as they roam, clothed in mist, all over the earth.