Exodus 24:18

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.

Surrounding context

24:17 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.

24:18 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.