Exodus 13:21-22

21As they travelled, the Lord was leading them. During the day, he was there as a pillar of cloud that went in front of them. During the night, he went as a pillar of fire. This gave them light, so they could travel during the day or the night.

22The cloud did not leave the people during the day. Nor did the fire leave them during the night. It was always in front of them.