19:9And the LORD said unto Moses, Lo, I come unto thee in a thick cloud, that the people may hear when I speak with thee, and believe thee for ever. And Moses told the words of the people unto the LORD.

19:16And it came to pass on the third day in the morning, that there were thunders and lightnings, and a thick cloud upon the mount, and the voice of the trumpet exceeding loud; so that all the people that was in the camp trembled.

24:16And the glory of the LORD 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.

24:17And the sight of the glory of the LORD was like devouring fire on the top of the mount in the eyes of the children of Israel.

24:18And Moses went into the midst of the cloud, and gat him up into the mount: and Moses was in the mount forty days and forty nights.