Sing praises to the LORD, Who dwells in Zion; declare His works among the nations.
MIDRASH TEHILLIM
1.....(9.12)
Interpretation of Rabbi Khanina: Sing praises to the Lord. When? When He comes to restore His presence to Zion.
RADAK
1. Sing praises to the LORD, Who dwells in Zion;
He says: which dwells in Zion, and that in spite of the fact that Zion was still in the hands of the Jebusites, because they had a tradition that the Glory should dwell there and the Sanctuary be built there; and Zion is the principal part (head) of Jerusalem.
2. declare His works among the nations.
In every place where you go, tell the doings and the wonders He worked among you.
Rabbi HIRSCH
1. Sing praises to the LORD - is Israel's call to all of its sons dispersed among the nations, charging them to gain inspiration, so that they might declare the greatness of God Who, in Zion, erected His Sanctuary that will one day benefit all of mankind, and Who still lets the throne of His world-wide sovereignty be borne by the Word laid down in Zion.
2. [עֲלִילָה] (alilah) is not a simple act, but a progression of a series of deeds.