Albert Barnes Commentary Psalms 104:9

"Thou hast set a bound that they may not pass over; That they turn not again to cover the earth." — Psalms 104:9 (ASV)

Thou hast set a bound that they may not pass over - See Job 26:10, note; Job 38:10–11, note.

That they turn not again to cover the earth - As it was before the dry land appeared; or as the earth was when darkness was upon the face of the deep (Genesis 1:2), and when all was mingled earth and water. It is possible that in connection with this, the psalmist may also have had his eye on the facts connected with the deluge in the time of Noah, and the promise then made that the world should no more be destroyed by a flood (Genesis 9:11; Genesis 9:15).