Exodus 13:20-22

They moved on from Succoth and then camped at Etham at the edge of the wilderness. GOD went ahead of them in a Pillar of Cloud during the day to guide them on the way, and at night in a Pillar of Fire to give them light; thus they could travel both day and night. The Pillar of Cloud by day and the Pillar of Fire by night never left the people.