"Narrated AbuSa’id al-Khudri {Radhi Allahu Anhu]: The Prophet (peace be upon him) said: A man should not look at the private parts of another man, and a woman should not look at the private parts of another woman. A man should not lie with a
nother man without wearing lower garment under one cover; and a woman should not be lie with another woman without wearing lower garment under one cover. (Sunan of Abu-Dawood – Book 31 Hadith 4007