'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 the way for themIn which they were to go.

You, in Your great mercy and compassion,Did not abandon them in the wilderness;The pillar of the cloud did not leave them by day,To lead them in the way,Nor the pillar of fire by night, to light for them the way they should go.