Charles Ellicott Commentary Psalms 104:10

"He sendeth forth springs into the valleys; They run among the mountains;" — Psalms 104:10 (ASV)

Springs. — The account in Genesis goes on abruptly from the appearance of the dry land to speak of the vegetation which covers it, apparently without any physical means for its production. But a poet, especially an Eastern poet, thinks first of the springs and rivers on which fertility and life depend. And such is his sympathy with nature that, disregarding the original record, he hastens to populate his world with creatures to share the Creator’s joy in its beauty and goodness.

Valleys. — i.e., the torrent beds, the “wadys” as the Arabs now call them.

Which run. — Better, they flow between the hills. The Septuagint supplies the subject “waters.”