Albert Barnes Commentary Psalms 77:17

"The clouds poured out water; The skies sent out a sound: Thine arrows also went abroad." — Psalms 77:17 (ASV)

The clouds poured out water - The marginal reading is: “The clouds were poured forth with water.” The translation in the text is more correct. This is a description of a storm, but it is not apparent to what particular storm in history this refers. It was evidently some exhibition of the divine greatness and power in delivering the children of Israel and may have referred to the extraordinary manifestation of God at Mount Sinai (Exodus 19:16), amidst lightnings, thunders, and tempests. For a general description of a storm, as illustrating this passage, see Job 36:26-33, notes; Job 37:1–5, notes; and Psalm 29:1-11.

The skies sent out a sound - The voice of thunder, which seems to come from the sky.

Thine arrows also - The lightnings—compared with burning or ignited arrows. Such arrows were anciently used in war. They were bound with rags and dipped in some combustible substance—such as turpentine—and shot into houses, grain-fields, haystacks, or towns for the purpose of setting them on fire. It was not unnatural to compare the rapid lightnings with such blazing arrows.

Went abroad - They moved rapidly in all directions.