This refers to prophets, officials, or possibly angels, who are constantly praying for the people of Jerusalem like watchmen who constantly guard the city. See what you used for "watchmen" in 52:8 and 56:10. (See: [[rc://en/ta/man/translate/figs-metaphor]])
## they are not silent day or night ##
This means they are continually pleading to God or calling to each other. (See: [[rc://en/ta/man/translate/figs-litotes]] and [[rc://en/ta/man/translate/figs-merism]])