|Amidah: Yom Yerushalayim: The Walls of Jerusalem|
The Holy One, Blessed is He, said: I and all my Heavenly Court will become a wall surrounding Jerusalem to protect it as the verse says, “Upon your walls, O Jerusalem, have I posted guardians (Isaiah 62:6).” [Pesikta Rabbati]
This reminds me of the following verses: “A song of ascents. Those who trust in God are like Mount Zion that falters not, but abides forever. Jerusalem, mountains enwrap it, and God enwraps His people, from this time and forever (Psalms 125:1-2)."
Jerusalem is surrounded by the Presence of God as a sign of His Divine protection. Therefore, when we recite this blessing of the Amidah, we are not only asking for Jerusalem the city but we are actually praying for the level of Divine protection symbolized by Jerusalem in these verses and midrash.