1)
What does this Mizmor discuss?
1.
Radak: David saw the gathering of exiles via Ru'ach ha'Kodesh.
2.
Malbim: After praising Hashem for good that applies to all His creations, he commands his Nefesh to thank for special good that he received.
2)
Why does it say "Hallelukah" and "Halleli Nafshi"?
1.
Radak: "Hallelukah" applies to Klal Yisrael; his Nefesh will praise Hashem with them.
