English Basic Explanation - Chapter 48
Psalm 48 is among the most festive of all the chapters of Tehillim, a prophetic song of praise for the beauty and splendor of the rebuilt city of Jerusalem during the time of the final redemption. Jerusalem is described as "Mesos Kol Ha'aretz" – a source of joy for the entire earth (verse 3) – which refers either to its elegance and climate (Radak) or the feeling of joy experienced by repentant sinners upon offering sacrifices (Rashi).
This era of glory is preceded by an attempt by enemy nations to wage war against the Jewish people, only to be vanquished by the Almighty's power (verses 5-8). Through the majesty and glory achieved by Jerusalem despite the enemies' efforts to destroy it, God will be once and for all recognized as the ultimate source of strength and protection on earth (verse 4). The glory of Jerusalem will serve as a reflection of the glory of God, who has chosen the city as His eternal seat of kingship.
This chapter concludes with exuberant declaration "Hu Yenahagenu Al-mut," which, according to several commentators, means that God will always care for the Jewish people with the tenderness and affection with which a parent cares for a child. The miraculous emergence of Jerusalem in the Messianic age as a city of unparalleled beauty and grandeur despite the assaults of our foes reassures us of the care and protection that God will eternally provide for Am Yisrael.
The Sages designated Psalm 48 as the chapter to be sung in the Bet Ha'mikdash on the second day of the week, and we thus recite it as the "Shir Shel Yom" every Monday. The Talmud (Rosh Hashanah 31a) explains, somewhat obscurely, "because [on the second day] He divided His creations and ruled over them." This refers to the fact that on the second day of creation God created the separation between heaven and earth (Bereshit 1:6-7), but it is unclear how this relates to chapter 48 of Tehillim. The Maharsha (Rabbi Shemuel Eliezer Eidels, Poland, 1555-1631) explained that the designation of Jerusalem as the seat of God's reign over the earth corresponds to the separation between heaven and earth. Just as God separated the world into two domains – heaven and earth – and then "dwelled" in the heavens and from there ruled over the earth, so did He set aside Jerusalem as His "city of residence" from where He exerts His authority over the entire world. Jerusalem, the city of God's abode, thus resembles the heavens, in that it is there where God sits on His throne, as it were, and rules over the rest of the earth.