What Does Exodus 14:21 Mean?

Then Moses stretched out his hand over the sea, and the LORD drove the sea back by a strong east wind all night and made the sea dry land, and the waters were divided. The sea opening's mechanics are described with dual causation: Moses stretches his hand (prophetic sign-action) and YHWH drives the sea back by a strong east wind (natural instrument of divine action).

The two descriptions are not contradictory but complementary: the wind is the physical mechanism through which YHWH acts; the wind is not a naturalistic explanation that eliminates the miraculous but the natural instrument of divine supernatural action. YHWH uses a real east wind to perform a real miracle.

The "strong east wind all night" creates the sea opening through a sustained overnight wind event: the waters are driven back, held back, and the sea bed becomes dry land. The specific direction (east) creates a crosswind scenario for Israel's passage (moving roughly north-south along the sea's narrower dimension through the wind-divided waters) or a direct into-the-sea wind that piles the water and exposes the bed. The details are consistent with the Sinai geography's known wind patterns while also being extraordinary in their precise timing and magnitude.

The "waters were divided" (Hebrew: vayibake'u hamayim, the waters were split) uses the same verb as God's creative separation of waters in Genesis 1:6-7. The sea crossing is a new creation act: YHWH who separated the waters at creation separates them again for Israel's passage. The creation-waters-separated theme is the theological background for the Red Sea as a new creation event: Israel walking through divided waters and emerging on the other side as a new covenant people is the narrative of a people's creation out of the chaotic sea, analogous to the creation of the world out of the original waters.