In the Masoretic Text, Psalm 93 lacks a superscription. The Septuagint, however, links the composition to David after the following: “For the day before the Sabbath, when the land was inhabited; praise of a song.”
Probably on account of a noteworthy act whereby YHWH revealed himself to be the Sovereign, the psalmist opened his composition with the words, “YHWH reigns.” As one “clothed” with majesty, the Most High is portrayed as arrayed with the dignity befitting a king. Girded with strength, he is in a position to take action. An evidence of his might is his having established the habitable land so that it is stable, not subject to being moved.
From of old, God’s “throne” (representative of his position as the supreme Sovereign) has been established, and this has been from the very start. He himself is eternal.
The “lifting up” of the “voice” of the rivers (probably to be understood of rivers at flood stage) suggests an intensification of the “sound” of their roaring. Lashing against the shore, the waves of the rapidly moving rivers exert tremendous force. The raging of “many” or abundant waters sounds like thunder. YHWH, in the height, is mightier than the “waves of the sea,” for he can restrain raging rivers and seas. The Septuagint reads, “Wondrous [are] the waves of the sea. The Lord [is] wondrous in [the] heights.”
In the Scriptures, enemy forces are spoken of as rivers that sweep over a land during campaigns of conquest. Possibly the reference to “rivers” in verse 3 alludes to this aspect. (Compare Isaiah 8:6-8.)
God’s “testimonies” or solemn charges are “very sure” or completely trustworthy, providing dependable guidance for what constitutes upright conduct. YHWH is holy, making it fitting for holiness or purity to be associated with his house or sanctuary. This should continue for “length of days,” or for all time to come.
Notes:
Regarding the divine name (YHWH), see Psalm 1.
For poetic effect, the Hebrew expression for “clothed” is repeated in the first verse.