Is sister-in law non-mahram?

- Can a man have a crush on the sister of his wife?

Dear Brother / Sister,

The sister-in-law of a man is temporarily non-mahram for him. A person cannot marry the sister of his wife; however, he can marry her if his wife dies. Otherwise, his sister-in-law is like a woman that is a stranger; it is necessary to be careful about the issues of privacy.     

A woman’s brother-in-law is non-mahram for him. That is, he is like a man that is a stranger. It is necessary to be careful about the issues of privacy.       

It is not permissible for a man to have a crush on his sister-in-law or any other non-mahram woman. It is necessary to be very careful about such relatives more than strangers. It is not permissible to remain alone with one’s sister-in-law/brother-in-law alone at home.

Once, the Prophet (pbuh) said,
"Avoid entering into places where women are." Somebody from Ansar asked, "O Messenger of Allah! What do you say about brothers-in-law (the relatives of the husband)?"
He said, "Brother-in-law is death." (see Bukhari, Nikah, III; Muslim, Salam, 20)

Imam Nawawi states the following in the explanation of this hadith:

"A man remains alone with the sister of his wife; that is death. The prohibition of talking with the brother-in-law is more necessary than strangers. That is the true meaning of the hadith."

It is necessary for a man to be careful about the boundaries of privacy related to his sister-in-law.

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