exodus 14:21 And Moses stretched out his hand over the sea; and the LORD caused the sea to go back by a strong east wind all that night, and made the sea dry land, and the waters were divided. - Free Bible Online

      21. Moses stretched out his hand, &c.--The waving of the rod was of great importance on this occasion to give public attestation in the presence of the assembled Israelites, both to the character of Moses and the divine mission with which he was charged.
      the Lord caused . . . a strong east wind all that night--Suppose a mere ebb tide caused by the wind, raising the water to a great height on one side, still as there was not only "dry land," but, according to the tenor of the sacred narrative, a wall on the right hand and on the left [Ex 14:22], it would be impossible on the hypothesis of such a natural cause to rear the wall on the other. The idea of divine interposition, therefore, is imperative; and, assuming the passage to have been made at Mount Attakah, or at the mouth of Wady Tawarik, an east wind would cut the sea in that line. The Hebrew word kedem, however, rendered in our translation, "east," means, in its primary signification, previous; so that this verse might, perhaps, be rendered, "the Lord caused the sea to go back by a strong previous wind all that night"; a rendering which would remove the difficulty of supposing the host of Israel marched over on the sand, in the teeth of a rushing column of wind, strong enough to heap up the waters as a wall on each side of a dry path, and give the intelligible narrative of divine interference.

JFB.