Exodus 24:16-18

16And the glory of Jehovah abode upon mount Sinai, and the cloud covered it six days: and the seventh day he called unto Moses out of the midst of the cloud. 17And the appearance of the glory of Jehovah was like devouring fire on the top of the mount in the eyes of the children of Israel. 18And Moses entered into the midst of the cloud, and went up into the mount: and Moses was in the mount forty days and forty nights.