Hadith 3100

Abu Sa'id reported God’s Messenger as saying, “A man must not look at a man’s private parts or a woman at a woman’s, and a man must not come close to a man in one garment or a woman to a woman in one garment.” Muslim transmitted it.

وَعَنْ أَبِي سَعِيدٍ قَالَ: قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: «لَا يَنْظُرُ الرَّجُلُ إِلَى عَوْرَةِ الرَّجُلِ وَلَا الْمَرْأَةُ إِلَى عَوْرَةِ الْمَرْأَةِ وَلَا يُفْضِي الرَّجُلُ إِلَى الرَّجُلِ فِي ثَوْبٍ وَاحِدٍ وَلَا تُفْضِي الْمَرْأَةُ إِلَى الْمَرْأَةِ فِي ثوب وَاحِد» . رَوَاهُ مُسلم

Reference: 5631000
In-book reference: Book 13, Hadith 3100