Hadith 338
'Abdul Rahman, the son of Abu Sa'id al-Khudri, reported from his father: 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.
Hadith 338
This hadith has been narrated by Ibn Abu Fudaik and Dabbik bin 'Uthman with the same chain of transmitters and they observed: Private parts of man are the nakedness (which is concealed).