The Messenger of Allah ﷺ said: A man should not see the private parts of another man, and a woman should not see the private parts of another woman, and a man should not lie with another man under one covering, and a woman should not lie with another woman under one covering.  

أَنَّ رَسُولَ اللَّهِ ﷺ قَالَ لاَ يَنْظُرُ الرَّجُلُ إِلَى عَوْرَةِ الرَّجُلِ وَلاَ الْمَرْأَةُ إِلَى عَوْرَةِ الْمَرْأَةِ وَلاَ يُفْضِي الرَّجُلُ إِلَى الرَّجُلِ فِي ثَوْبٍ وَاحِدٍ وَلاَ تُفْضِي الْمَرْأَةُ إِلَى الْمَرْأَةِ فِي الثَّوْبِ الْوَاحِدِ  

Private parts of man are the nakedness (which is concealed).  

أَخْبَرَنَا الضَّحَّاكُ بْنُ عُثْمَانَ بِهَذَا الإِسْنَادِ وَقَالاَ مَكَانَ عَوْرَةِ عُرْيَةِ الرَّجُلِ وَعُرْيَةِ الْمَرْأَةِ