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." (JA)
English reference (JA): Vol. 1, Book 1, Hadith 661 (JA)
Arabic reference (JA): Book 1, Hadith 706 (JA)