Prohibition of gazing at women and Beardless Handsome Boys except in Exigency — Riyad as-Salihin 1627

The Messenger of Allah (ﷺ) said, "A man must not look at a man's private parts nor must a woman look at a woman's private parts; neither should two men lie naked under one cover, nor should two women lie naked under the same cover."[Muslim].