Let the floods clap their hands,.... Or "rivers" , dashing against their banks, as they pass along; a prosopopoeia, as the preceding and following, expressing great joy on account of the Messiah, the reigning King.
Aben Ezra interprets this of men that are in rivers, as the sea; in the preceding verse of such that are in ships at sea; and the hills in the next clause of such that dwell on them;let the hills be joyful together; see Isa 55:12.