Literally, “keeps faithfulness,” that is, “remains faithful.”
The righteous nation.
Jerusalem will be called “The city of righteousness, the faithful city” (ch. 1:26), because its inhabitants will all be holy and righteous. Only those who are loyal to God and who serve Him with faithfulness can expect to “enter in through the gates into the city” (Rev. 22:14; see on Matt. 7:21-27).