Psalms 104:9

Thou hast set a bound that they may not pass - And what is this bound? The flux and reflux of the sea, occasioned by the solar and lunar attraction, the rotation of the earth on its own axis, and the gravitation of the waters to the center of the earth. And what is the cause of all these? The will and energy of God. Thus the sea is prevented from drowning the earth equally where there are flat shores as where the sea seems hemmed in by huge mounds of land and mountains. The above, not these, are the bounds which it cannot pass, so that they cannot turn again to cover the earth.

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.

104:9 A bound - Even the sand of the sea - shore.