This refers to the people assigned to each gate, responsible to control access to the city or temple, as well as to open and close the gates at times and for reasons set by the administrator. See how you translated this in [Nehemiah 7:1](../07/01.md).
This phrase can be made explicit. AT: "all who were old enough to understand what promising to obey God meant" (See: [[rc://en/ta/man/translate/figs-explicit]])