Albert Barnes Commentary Psalms 114:3

"The sea saw it, and fled; The Jordan was driven back." — Psalms 114:3 (ASV)

The sea saw it - The word "it" is supplied by our translators, although not very appropriately. It would be more expressive to say, “The sea saw:” that is, the sea (the Red Sea) saw the mighty movement, the marshalled hosts, the moving masses, the cattle, the pursuing enemies, the commotion, the agitation, on its usually quiet shores.

We are to imagine the usual calmness of the desert—the waste and lonely solitudes on the banks of the Red Sea—and then all this suddenly broken in upon by vast hosts of men, women, children, and cattle, fleeing in consternation, followed by the embattled strength of Egypt, all rolling tumultuously to the shore.

No wonder that the sea is represented as astonished at this unusual spectacle and as fleeing in dismay.

And fled - As if frightened at the approach of such a host, coming so suddenly upon its shores.

Jordan was driven back - This refers to the dividing of the waters of the Jordan when the children of Israel passed over to the promised land (Joshua 3:13–17). They also seemed astonished at the approach of the Hebrews and retired to make a way for them to pass over.