Sunan Ibn Majah, Hadith 661 ⓘ
It was narrated from 'Abdur-Rahman bin Abu Sa'eed Al-Khudri from his father that: The Messenger of Allah said: "No woman should look at the nakedness of another woman, and no man should look at the nakedness of another man."
حَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ، حَدَّثَنَا زَيْدُ بْنُ الْحُبَابِ، عَنِ الضَّحَّاكِ بْنِ عُثْمَانَ، حَدَّثَنَا زَيْدُ بْنُ أَسْلَمَ، عَنْ عَبْدِ الرَّحْمَنِ بْنِ أَبِي سَعِيدٍ الْخُدْرِيِّ، عَنْ أَبِيهِ، أَنَّ رَسُولَ اللَّهِ ـ صلى الله عليه وسلم ـ قَالَ " لاَ تَنْظُرِ الْمَرْأَةُ إِلَى عَوْرَةِ الْمَرْأَةِ وَلاَ يَنْظُرِ الرَّجُلُ إِلَى عَوْرَةِ الرَّجُلِ " .
also referenced under: Book 1, Hadith 706 (In-Book) & Volume 1, Book 1, Hadith 661 (DarusSalam)