Albert Barnes Commentary Psalms 105:39

"He spread a cloud for a covering, And fire to give light in the night." — Psalms 105:39 (ASV)

He spread a cloud for a covering - See the notes at (Psalms 78:14). In (Numbers 10:34), it is said that the cloud of the Lord was upon them by day, and from this seems to have been derived the idea of its covering them, as if it were a protection from the heat in the desert.