"No doubt! They did fold up their breasts, that they may hide from Him. Surely, even when they cover themselves with their garments, He knows what they conceal and what they reveal. Verily, He is the All-Knower of the (innermost secrets) of the breasts." (V.11:5)
Reference
Sahih al-Bukhari 4681
In-book reference
Book 65, Hadith 203
USC-MSA web (English)
Vol. 6, Book 60, Hadith 203
Arabic Text
حَدَّثَنَا الْحَسَنُ بْنُ مُحَمَّدِ بْنِ صَبَّاحٍ، حَدَّثَنَا حَجَّاجٌ، قَالَ قَالَ ابْنُ جُرَيْجٍ أَخْبَرَنِي مُحَمَّدُ بْنُ عَبَّادِ بْنِ جَعْفَرٍ، أَنَّهُ سَمِعَ ابْنَ عَبَّاسٍ، يَقْرَأُ {أَلاَ إِنَّهُمْ تَثْنَوْنِي صُدُورُهُمْ} قَالَ سَأَلْتُهُ عَنْهَا فَقَالَ أُنَاسٌ كَانُوا يَسْتَحْيُونَ أَنْ يَتَخَلَّوْا فَيُفْضُوا إِلَى السَّمَاءِ، وَأَنْ يُجَامِعُوا نِسَاءَهُمْ فَيُفْضُوا إِلَى السَّمَاءِ، فَنَزَلَ ذَلِكَ فِيهِمْ.