A Commentary, Critical, Practical, and Explanatory on the Old and New Testaments, by Robert Jamieson, A.R. Fausset and David Brown  at sacred-texts.com
psa 99:1God's government is especially exercised in and for His Church, which should praise Him for His gracious dealings. (Psa 99:1-9)
sitteth . . . cherubim--(compare Sa1 4:4; Psa 80:1).
tremble . . . be moved--inspired with fear by His judgments on the wicked.
psa 99:2great in Zion--where He dwells (Psa 9:11).
psa 99:3thy . . . name--perfections of justice, power, &c.
great and terrible name--producing dread (Deu 10:17), and to be praised by those over whom He is exalted (Psa 97:9).
it is holy--or, "He is holy" (Psa 99:5, Psa 99:9; Isa 6:3).
psa 99:4To His wise and righteous government all nations should render honor.
king's . . . judgment--His power is combined with justice.
he is holy--(compare Psa 22:3).
psa 99:6The experience of these servants of God is cited for encouragement.
among . . . priests, among . . . upon the Lord [and] He spake . . . pillar--may be referred to all three (compare Exo 18:19; Lev 8:15; Deu 5:5; Sa1 9:13).
psa 99:7cloudy pillar--the medium of divine intercourse (Exo 33:9; Num 12:5). Obedience was united with worship. God answered them as intercessors for the people, who, though forgiven, were yet chastened (Exo 32:10, Exo 32:34).