Exodus 24:15-18

Then Moses went up into the mountain, and a cloud covered the mountain. Now the glory of the LORD rested 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. The sight of the glory of the LORD was like a consuming fire on the top of the mountain in the eyes of the children of Israel. So Moses went into the midst of the cloud and went up into the mountain. And Moses was on the mountain forty days and forty nights.