That he heard Ibn `Abbas reciting: "No doubt! They fold up their breasts." (11.5) and asked him
about its explanation. He said, "Some people used to hide themselves while answering the call of
nature in an open space lest they be exposed to the sky, and also when they had sexual relation with
their wives in an open space lest they be exposed to the sky, so the above revelation was sent down
regarding them."
Sahih al-Bukhari Book 65, Hadith 203