حَدَّثَنَا الْحَسَنُ بْنُ مُحَمَّدِ بْنِ صَبَّاحٍ، حَدَّثَنَا حَجَّاجٌ، قَالَ قَالَ ابْنُ جُرَيْجٍ أَخْبَرَنِي مُحَمَّدُ بْنُ عَبَّادِ بْنِ جَعْفَرٍ، أَنَّهُ سَمِعَ ابْنَ عَبَّاسٍ، يَقْرَأُ ‏ Begin hadith 9‏ قَالَ سَأَلْتُهُ عَنْهَا فَقَالَ أُنَاسٌ كَانُوا يَسْتَحْيُونَ أَنْ يَتَخَلَّوْا فَيُفْضُوا إِلَى السَّمَاءِ، وَأَنْ يُجَامِعُوا نِسَاءَهُمْ فَيُفْضُوا إِلَى السَّمَاءِ، فَنَزَلَ ذَلِكَ فِيهِمْ‏.‏

Narrated Muhammad bin `Abbas bin Ja`far: 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." Translation Not Available

Book Ref: Sahih Bukhari Book 65 Hadith 4681
Web Ref:  Sahih Bukhari Vol 6 Book 60 Hadith 203