Charles Spurgeon Commentary Exodus 14:16-20

"And lift thou up thy rod, and stretch out thy hand over the sea, and divide it: and the children of Israel shall go into the midst of the sea on dry ground. And I, behold, I will harden the hearts of the Egyptians, and they shall go in after them: and I will get me honor upon Pharaoh, and upon all his host, upon his chariots, and upon his horsemen. And the Egyptians shall know that I am Jehovah, when I have gotten me honor upon Pharaoh, upon his chariots, and upon his horsemen. And the angel of God, who went before the camp of Israel, removed and went behind them; and the pillar of cloud removed from before them, and stood behind them: and it came between the camp of Egypt and the camp of Israel; and there was the cloud and the darkness, yet gave it light by night: and the one came not near the other all the night." — Exodus 14:16-20 (ASV)

God was like a wall of fire between them and their enemies, so that they had no cause for fear even though the Egyptians were so near.