the Prophet (peace and blessings of Allaah be upon him) said: “Beware of entering upon women.” A man from among the Ansaar said, “What about the in-law, O Messenger of Allaah?” He said, “The in-law is death.”
Narrated by al-Bukhaari, 5232; Muslim, 2172.
This could only have been by a Prophet of God indeed. I consider this Hadith a scientific miracle, those who know and hear about what goes on in the Hindu communities where the entire family lives in one house and there is no hijaab/niqaab/segregation whatsoever among them would agree with me, some really bizarre cases occur where wives have relationships with their brother-in-laws.....!!!
People usually take such things lightly because they trust each other, but the shaitaan (devil) is an evil being and can cause trouble when a woman and her in-law are alone...