וְאַֽל־תִּתְּנ֥וּ דֳמִ֖י ל֑וֹ עַד־יְכוֹנֵ֞ן וְעַד־יָשִׂ֧ים אֶת־יְרֽוּשָׁלִַ֛ם תְּהִלָּ֖ה בָּאָֽרֶץ׃
也不要讓祂歇息,直到祂堅立耶路撒冷,使耶路撒冷在地上成為人們稱頌的城。
Shenei Luchot HaBerit
I have found in the book Ba-assarah ma-amorot chapter 3, an article that explains the source of this legislation. The author writes as follows, quoting Isaiah 62,6: "Upon your walls O Jerusalem, I have set watchmen." These are four watchmen corresponding to the four-lettered name of G–d, their דינים are three, since the watchmen of the "Upper World" never abandon Jerusalem, and concerning them the prophet says "all day long and all night long" (ibid.). They are never without supervision.