Exodus 14:19-20

The angel of God, who had been going in front of the camp of Israel, moved and went behind them. The pillar of the cloud moved from in front and stood behind them. So it came between the camp of Egypt and the camp of Israel. It was a cloud along with darkness [even by day to the Egyptians], but it gave light by night [to the Israelites]; so one [army] did not come near the other all night.