Deuteronomy 5:4

Deuteronomy 5:4 (New International Version)

⁴ The LORD spoke to you face to face out of the fire on the mountain.

This verse clears something up for me about how Moses could speak with God face to face, as you would with a friend, and not perish.

"face to face out of the fire"

Although they were face to face there was a covering to protect them from actually seeing God's face.