Rabbi Roodyn

י) אִמְרוּ בַגּוֹיִם ה’ מָלָךְ אַף תִּכּוֹן תֵּבֵל בַּל תִּמּוֹט יָדִין עַמִּים בְּמֵישָׁרִים:

Say among the nations, “Hashem has reigned.” Also the inhabited world will be established so that it will not falter; He will judge peoples with equity.

Rashi says that this is the song that will be uttered in the future when all of humanity will come to the recognition of Hashem. The Seforno adds that their recognition will be retroactive, presumably meaning that they will look back and see Hashem’s guiding Hand in all of history.

The Radak explains that the phrase “Also the inhabited world will be established” refers to the era of world peace that will be ushered in with the coming of Moshiach. This will come as a result of the nations of the world recognising Hashem’s power which will be made apparent from the way that He will redeem the Jewish people from exile. The glory of the Jewish people returning home and the miraculous defeat of the nations who will attempt to attack Yerushalayim (in the war of Gog and Magog) will make Hashem’s power clear for all to see.

As a result of this clarity we will witness the fulfilment of the Micha’s famous prophecy (4:3) “And he shall judge between many peoples and reprove mighty nations afar off; and they shall beat their swords into plowshares, and their spears into pruning hooks; nations shall not lift the sword against nation; neither shall they learn war anymore”.