Jami` at-Tirmidhi Book 43, Hadith 66
"The Messenger of Allah (ﷺ) said: 'A man is not to look at the 'Awrah of a man, and a woman is not to look at the 'Awrah of a woman. A man is not to be alone with a man under one garment, and a woman is not to be alone with a woman under one garment.'"
that the Messenger of Allah (ﷺ) said: "A woman is not to touch a woman such that she can describe her to her husband as if he is looking at her."
from his father, from his grandfather, who said: "I said: 'O Prophet of Allah! Regarding our 'Awrah, what of it must we cover and what of it may we leave?' He said: 'Protect your 'Awrah except from your wife or what your right hand possesses.' He said: "I said: 'O Messenger of Allah! What about when some people are with others?' He said: 'If you are able to not let anyone see it then do not let them see it.'" He said: "I said: 'O Prophet of Allah! What about when one of us is alone?' He said: 'Allah is more deserving of being shy from Him than the people.'"