'Pillar of Fire' in the Bible

“And with a pillar of cloud You led them by day,And with a pillar of fire by nightTo light for them the wayIn which they were to go.

You, in Your great compassion,Did not forsake them in the wilderness;The pillar of cloud did not leave them by day,To guide them on their way,Nor the pillar of fire by night, to light for them the way in which they were to go.