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 how you translated "watchmen" in [Isaiah 52:8](../52/08.md) and [Isaiah 56:10](../56/10.md). (See: [[rc://en/ta/man/translate/figs-metaphor]])
This means they are continually pleading to Yahweh or calling to each other. Alternate translation: "they are earnestly praying to Yahweh throughout the entire day" (See: [[rc://en/ta/man/translate/figs-litotes]] and [[rc://en/ta/man/translate/figs-merism]])