Who should elevate "Hashem Elokeinu"?
Radak: Yisrael and the nations. Elevate Him verbally!
What is "Hadom Raglav"?
Radak: It is the Beis ha'Mikdash.
Malbim: It is the end of His Hashgachah. Even though now it discusses when Hashem does not dwell in the land to conduct by Himself, rather, His Kisei is in Shamayim, and the miracles are hidden and descend via Shamayim and nature. Hadom Raglav is in the land, via Shamayim. He arranges conduct of the Kisei and sitting on it (conducting the Ma'arachah) according to Hadom Raglav and the need in the land, according to deed and needs of the lower beings. Therefore you should bow to Hadom Raglav, for the end of the causes is there according to Hashgachah Pratis.
What is "Kadosh"?
Radak: Hashem and His name. You see that early Nevi'im, who were Kedoshim, when they bowed to Him and prayed to Him, He answered them.
Malbim: He is separated and conducts according to Hashgachah and wonders. It says "Kadosh Hu" in the third person (even though verses 3-4 were in second person), for at this level His Kedushah is still wrapped and covered in the veil of nature.
