Dora Bas Rivka Silver O'H
Hashem Tzivakos Imanu...
The sons of Korach composed this Psalm and it is meant to be accompanied by an instrument called an alamos. (The name of this instrument may involve wordplay on "al mus," "beyond death," the closing words of Psalm 48, also by the sons of Korach.)
G-d is a source of defense and strength in times of trouble. We should not fear any earthly cataclysm or upheaval, as we have seen His salvations in the past and we know what to expect. The whole world may be turned upside-down, either literally or figuratively, and the results will proclaim G-d's glory. Amidst the chaos, a clear stream - possibly representing Torah - will gladden the inhabitants of Jerusalem. G-d makes Himself felt there and it will not suffer the same collapse as the rest of the world. (The Psalm says He will help them at dawn; this is interpreted to mean in the merit of Abraham, who would rise at dawn to pray to G-d.)
The nations cry out in protest - they just can't believe it! - but they ultimately fall. G-d raises His "voice" and they melt before Him. But He is with us and is a fortress of protection for us. (Here, He is called the G-d of Jacob, who was continuously tested throughout his life.) Go see G-d's wonders throughout the land; He has felled mighty armies and ended their aggression throughout the world. He destroys their weapons and ends their assaults, so they must recognize that He is G-d. He is above all.
The Psalm ends by repeating that the G-d of Jacob is with us and always protects us. This verse ("Hashem tzivakos imanu, misgav lanu Elokei Yaakov selah) may be familiar as it is recited daily in the morning prayer "Hodu," plus in "V'Atoh Kadosh" at the conclusion of Shabbos.