Exodus 13:20-22

20After leaving Sukkoth they camped at Etham on the edge of the desert. 21By day the LORD went ahead of them in a pillar of cloud to guide them on their way and by night in a pillar of fire to give them light, so that they could travel by day or night. 22Neither the pillar of cloud by day nor the pillar of fire by night left its place in front of the people.