Genesis 2:25 (ESV)

25 And the man and his wife were both naked and were not ashamed.

The unity of life in paradise between Adam and his wife was such that they could walk around naked. There was nothing between them that brought separation or shame. They trusted each other completely. They lived in tender love for each other. There was nothing that served as a threat to the other. There was no fear of the other. For us who are living after the fall, this nakedness is a sign of their pure relationship.