What should He do for David?
Radak: You appeared to him in this place with fire of Your honor, and revealed to him that this is the chosen place. For him, make this the place forever. Avodas ha'Kohanim and song of the Leviyim should not cease from it.
Malbim: The choice of the Mikdash to dwell there permanently was due to David and his merit, i.e. (a) due to his Avodah, and (b) because he was chosen and anointed - "Matzasi David Avdi b'Shemen Kadshi Meshachtiv" (89:21). Also in Divrei ha'Yamim II, 6:42 it says "Al Tashev Pnei Meshichecha Zachrah l'Chasdei David Avdecha."
To what does "Al Tashev Pnei Meshichecha" apply?
Rashi: When Shlomo will come to enter the Aron 1 [to the Kodesh ha'Kodoshim, do not reject him].
Radak: What I pray about this place, and what Shlomo will pray, accept our Tefilos. Shlomo said essentially these verses at the end of his Tefilah (Divrei ha'Yamim II, 6:41-42).
Shabbos 30a: When Shlomo wanted to bring the Aron into the Kodesh ha'Kodoshim, the gates clung to each other
