Does this literally discuss Yerushalayim's walls?
Rashi, based on Targum Yonasan: The walls are the first Avos; they protect over us like a wall.
Radak: Yes. Hashem tells Yerushalayim, after your walls will be built, do not fear lest they fall again. I appointed guards over them constantly, day and night.
Who are the guards?
Rashi citing Menachos 87a: They are angels.
Radak #1: They are those who mourn over Yerushalayim, and pray day and night for it.
Radak #2: They are all Yisrael in Galus. They constantly wait for the building of Yerushalayim, and mention it day and night in their Tefilos and Brachos.
Radak: This is a metaphor for Hashem's Hashgachah, like "Einei Hashem Elokecha Bah me'Reishis ha'Shanah Ad Acharis Shanah" (Devarim 11:12).
Malbim (7): They are the Nevi'im and Tzadikim in every generation.
What is the consequence of "Tamid Lo Yecheshu" (they are never silent)?
Rashi citing Menachos 87a #1: They constantly say "Atah Sakum Terachem Tziyon 1 " (Tehilim 102:4).
Rashi citing Menachos 87a #2: They constantly say "Boneh Yerushalayim Hashem" (Tehilim 147:2).
Rashi: They write chronicles, so [Yisrael's] merit will not be forgotten. They are never silent from mentioning their merit in front of Me.
Radak: Other wall guards, if they are awake at night, they do not cease talking; each makes his friend awake. During the day they sleep. The guards of Yerushalayim's walls are always awake, day and night.
Malbim: Hashem said "Lema'an Tziyon Lo Echesheh" (1). Additionally, He placed guards ready for the day [when the walls will be built]. Do not say that they will be quiet until then!
87a: Before the Churban, they said "Ki Vachar Hashem b'Tziyon Ivah l'Moshav Lo" (Tehilim 132:13).
Who are "ha'Mazkirim Es Hashem"?
Rashi: They are angels [who mention Zechus Avos].
Radak: They are Bnei Galus. It is upon them to be Mazkir Es Hashem!
Who says "ha'Mazkirim Es Hashem
Radak #1: These are Hashem's words 1 , like "Shuvu Banim Shovavim Erpa Meshuvoseichem Hinenu Asanu Lach Ki Atah Hashem Elokeinu" (Yirmeyah 3:22). He makes them zealous to repent.
Radak #2: The Navi says so for Bnei Galus. He says, since he makes all these good promises for you, mention His name constantly. Pour out your hearts in front of Him, until He gathers the exiles, founds Yerushalayim and makes it praise in the land.
Radak: Even though the verse was in first person (Hifkadti), it says "Es Hashem" (and not 'Osi'); verses often do so, e.g. "v'El Moshe Amar Aleh El Hashem" (Shemos 24:1).
What is the meaning of "Al Dami Lachem"?
Rashi: Do not be silent.
Radak: Do not cease praying in front of Him constantly. Pour out your hearts in front of Him, until He founds Yerushalayim with its walls and buildings, and makes it praise in the land. Now in Galus, it is the opposite - it is a disgrace and a mockery to the nations.
