Commentary on the Bible, by Adam Clarke, [1831], at sacred-texts.com
The empire of God in the world and the Church, Psa 99:1, Psa 99:2. He ought to be praised, Psa 99:3. Justice and judgment are his chief glory, Psa 99:4. He should be worshipped as among the saints of old, whom he graciously answered and saved, Psa 99:5-8. Exalt him because he is holy, Psa 99:9.
The Hebrew and Chaldee have no title; all the versions but the Chaldee attribute it to David. The Syriac says it concerns "the slaughter of the Midianites which Moses and the children of Israel had taken captive; and is a prophecy concerning the glory of the kingdom of Christ." But the mention of Samuel shows that it cannot be referred to the time of Moses. Calmet thinks that it was sung at the dedication of the city, or of the second temple, after the return from the Babylonish captivity. Eight of Kennicott's and De Rossi's MSS. join it to the preceding psalm.
The Lord reigneth - See the note on Psa 97:1.
Let the people tremble - He will establish his kingdom in spite of his enemies; let those who oppose him tremble for the consequences.
He sitteth between the cherubims - This is in reference to the ark, at each end of which was a cherub of glory; and the shechinah, or symbol of the Divine Presence, appeared on the lid of the ark, called also the mercy-seat, between the cherubim. Sitting between the cherubim implies God's graciousness and mercy. While then, in his reign, he was terrible to sinners, he is on the throne of grace to all who fear love, and obey him. Though this symbol were not in the second temple, yet the Divine Being might very well be thus denominated, because it had become one of his titles, he having thus appeared under the tabernacle and first temple.
The Lord is great in Zion - It is among his own worshippers that he has manifested his power and glory in an especial manner. There he is known, and there he is worthily magnified.
Let them praise thy great and terrible name - Let them confess thee to be great and terrible: let them tremble before thee.
For it is holy - קדוש הוא kadosh hu. As this not only ends this verse but the fifth also, and in effect the ninth, it seems to be a species of chorus which was sung in a very solemn manner at the conclusion of each of these parts. His holiness - the immaculate purity of his nature, was the reason why he should be exalted, praised, and worshipped.
The king's strength - If this Psalm were written by David, he must mean by it that he was God's vicegerent or deputy, and that, even as king, God was his strength, and the pattern according to which equity, judgment, and righteousness should be executed in Jacob.
Worship at his footstool - Probably meaning the ark on which the Divine glory was manifested. Sometimes the earth is called God's footstool, Mat 5:35; Isa 66:1; sometimes Jerusalem; sometimes the temple, Lam 2:1; sometimes the tabernacle, Psa 32:7; and sometimes the ark, Ch1 28:2. The Israelites, when they worshipped, turned their faces toward the ark, because that was the place where was the symbol of the Divine Presence.
For he is holy - The burden chanted by the chorus.
Moses and Aaron - As Moses and Aaron among the priests, and as Samuel among the prophets, worshipped God in humility, gratitude, and the spirit of obedience, and received the strongest tokens of the Divine favor; so worship ye the Lord, that he may bless, support, and save you. Moses was properly the priest of the Hebrews before Aaron and his family were appointed to that office.
He spake unto them in the cloudy pillar - That is, he directed all their operations, marchings, and encampments by this cloudy pillar. See Exo 33:9.
They kept his testimonies - Do ye the same, and God will be your portion as he was theirs.
Thou - forgavest them - When the people had sinned, and wrath was about to descend on them, Moses and Aaron interceded for them, and they were not destroyed.
Tookest vengeance of their inventions - God spared them, but showed his displeasure at their misdoings. He chastised, but did not consume them. This is amply proved in the history of this people.
Worship at his holy hill - Worship him publicly in the temple.
For the Lord our God is holy - The words of the chorus; as in the third and fifth verses.