Sayyiduna Abu Sa'id Khudri (may Allah be pleased with him) narrates that the Prophet (peace and blessings of Allah be upon him) said: "No man should look at the private parts of another man, and no woman should look at the private parts of another woman. No man should lie with another man under a single garment (while naked), and no woman should lie with another woman under a single garment (while naked)."