Exodus 24:16-18

16And the glory of Jehovah abode on mount Sinai, and the cloud covered it six days; and on the seventh day he called to Moses out of the midst of the cloud. 17And the appearance of the glory of Jehovah was like a consuming fire on the top of the mountain, before the eyes of the children of Israel. 18And Moses went into the midst of the cloud, and ascended the mountain. And Moses was on the mountain forty days and forty nights.