Western Saints
Augustine of Hippo
"The floods lift up their voices" [Psalm 93:3]. What are these floods, which have lift up their voices? We heard them not: neither when our Lord was born, did we hear rivers speak, nor when He was baptized, nor when He suffered; we heard not that rivers did speak. Read the Gospel, you find not that rivers spoke. It is not enough that they spoke: "They have lift up their voice:" they have not only spoken, but bravely, mightily, in a lofty voice. …
Exposition on Psalm 93 ↗
Jerome
The floods have lifted up, O Lord, they have lifted up their voices; from the voices of many waters, wonderful are the surgings of the sea. As many words, so many meanings: as many little verses, so many sacraments. The floods have lifted up their voices. This is what is said in another place: 'The rush of the river maketh glad the city of God.' And in another place: 'The rivers shall clap their hands together.' The floods seem to me to be those which water the whole world, the apostolic and prophetic dignities. …
Homily 70, on Psalm 92 (Alternate Series) ↗
Bonaventure
The spiritual meanings are called rivers — and also those men who understand in a spiritual manner — because they have their origin from the Scriptures and are confirmed by the Scriptures, and because, from these spiritual meanings, other meanings are derived. Hence in the Psalm: "The floods lift up, O Lord, the floods lift up their voice; the floods lift up their tumult. More powerful than the roar of many waters." Why? Because "powerful on high is the Lord," God's voice had to be loud.
Collations on the Hexaemeron, Collation 13 ↗