Albert Barnes Commentary Job 38:9

"When I made clouds the garment thereof, And thick darkness a swaddling-band for it," — Job 38:9 (ASV)

When I made the cloud the garment thereof - Referring to the garment in which the new-born infant is wrapped up. This image is one of great beauty. It is that of the vast ocean just coming into being, with a cloud resting upon it and covering it.

Thick darkness envelopes it, and it is swathed in mists; compare Genesis 1:2, And darkness was upon the face of the deep. The time here referred to is that before the light of the sun arose upon the earth, before the dry land appeared, and before animals and people had been formed.

Then the new-born ocean lay carefully enveloped in clouds and darkness under the guardian care of God. The dark night rested upon it, and the mists hovered over it.