Exodus 24:16-20

The glory of the Lord settled on Mount Sinai, and the cloud covered it for six days; and on the seventh day He called to Moses from the midst of the cloud.

And to the eyes of the sons of Israel, the appearance of the glory of the Lord was like a consuming fire on the mountain top.

Then Moses entered the midst of the cloud as he went up to the mountain; and Moses was on the mountain for forty days and forty nights.