שַׁבַּחוּ קֳדָם יְיָ תּוּשְׁבַּחְתָּא חֲדְתָּא שַׁבַּחוּ אַנְגְלֵי מְרוֹמָא שַׁבַּחוּ קֳדָם יְיָ כָּל צַדִיקֵי אַרְעָא.
1. Sing to Hashem a new song | שִׁירוּ לַי"י שִׁיר חָדָשׁ – This psalm is almost identical to Divrei HaYamim I 16:23-33, the song sung when the ark was taken from the house of Oved Edom to the City of David. Radak suggests that our psalm slightly adapts the original and applies it to Messianic times and the ingathering of exiles; as such the psalmist opens with the cry to sing a "new" song (see Rashi and Sforno as well). Cf. the commentary attributed to Rashbam that the hymn was sung when Shelomo brought the ark into the Beit HaMikdash, pointing to verse 6, "עֹז וְתִפְאֶרֶת בְּמִקְדָּשׁוֹ" (might and glory in His sanctuary), as support. The psalm's main theme is God's greatness and righteous kingship over all.
2. all the earth | כׇּל הָאָרֶץ – See Radak that this is short for: "all the inhabitants of the earth ". Cf. Ibn Ezra on verse 3 that though the term "כׇּל הָאָרֶץ" generally refers to inhabitants of the world at large, since verse 3 speaks of recounting God's glory amongst the nations, this verse might refer specifically to the Land of Israel. According to him, then, the psalmist first calls to Israel to sing to God and then turns to the rest of the world.