Exodus 14:19-21a:

Then the angel of God, who was leading the Israelites, moved to their rear—the pillar of cloud left the front of their number and took up position behind them, between the Israelites and the Egyptians. All during the night the cloud provided light to one side and darkness to the other side, so that there was no contact between them. Then Moses stretched his hand over the sea, and YHWH swept the sea with a strong east wind throughout the night and so turned it into dry land.