Does a woman have to observe Purdah for her father-inlaw?

Answer

It depends what is understood by Purdah. A daughter-in -law may appear in the presence of her father-in-law without niqaab and without burqah. However, she should be modestly dressed and not be alone with him. He is not an appropriate mahram for her on a journey. If she had not married his son, then he (the father-in-law) could have married her. This is sufficient to understand that the lust of the nafs is ever present, hence, she must be wary of her father-in-law. At most he may make musaafahah with her. However, if even handshaking creates desire in him, then shaking hands with her will be haraam. Too many cases of misdemeanour happen between women and their fathers-in-law. She should not provide any occasion which could entice her father-in-law.