Exodus 14:20

and it came between the camp of the Egyptians and the camp of Israel; and it was a cloud and darkness to them (the Egyptians), but it gave light by night to these, the children of Israel; in its protecting capacity the cloud revealed a double character, an effectual barrier of impenetrable darkness to the enemies, a cheering and comforting light to the believers, so that the one came not near the other all the night.