He gave his wife money to do Hajj then he died; is it permissible for her to use it for something other than Hajj?
Question

                A husband paid hajj for his wife, a month to that hajj, the man passed on. Is the wife allowed to perform that hajj or collect the money back for her personal use? what are the reason for her to perform the hajj or to collect back the paid money?.
Praise be to Allah.
    Yes, the wife has to do Hajj with this money whenever she is 
    able to and has a mahram, because the husband only gave her the money to do 
    Hajj with it. It seems that if he knew that she would not do Hajj with the 
    money he would not have given it to her. The basic principle with regard to 
    donated money is that it should be spent on the charitable causes stipulated 
    by the giver, and it should not be spent on anything else, unlike general 
    donations which are not intended for any specific purpose, so they may be 
    spent on all kinds of charitable causes. 

    Shaykh Zakariya al-Ansaari (may Allah have mercy on him) 
    said: 

    If he gives him some money and tells him: Buy yourself a 
    turban with it or use it to go to the public bath (hammam) and so on, then 
    it is specifically for that purpose, because that was the intention of the 
    one who gave the money, as he intended that he should cover his head with 
    the turban and clean himself by going to the hammam, because he saw that he 
    was bareheaded and that his body was unkempt and dirty. Otherwise, if he did 
    not intend that exactly, such as if he said it by way of ordinary chitchat, 
    then he does not have to use the money for that particular purpose, rather 
    he may take possession of it and dispose of it in whatever way he wants.

    End quote. Asna’l-Mataalib Sharh Rawdat al-Taalib, 
    2/479-480 

    Shaykh Sulaymaan ibn ‘Umar al-Jamal (may Allah have mercy on 
    him) said: 

    If he gives him dates with which to break the fast, then he 
    must use them for that purpose, and it is not permissible to use them for 
    any other purpose, because the intention of the giver was specific. End 
    quote. 

    Haashiyat al-Jamal ‘ala Sharh al-Manhaj, 
    2/328 

    And Allah knows best.