Psalms 55:10

they go about it upon the walls thereof A metaphor from watchmen going their rounds on the city walls. But who are meant by they?Perhaps the party hostile to the Psalmist, who are ever patrolling the city, on the alert for mischief. Cp. Isaiah 29:20. But perhaps rather Violence and Strife personified. These he implies with a bitter irony are the watchmen who are now in charge of order and safety in the city. This explanation agrees well with the following lines:

Iniquity also and Mischief are in the midst of it,

Destruction is in the midst thereof:

Oppression and Deceit depart not from her streets.