Her mother died and she had vowed to sacrifice a sheep; can her daughter give the cash value instead?
Question

                Her maternal uncle was in an accident and her mother had vowed that if he got out safely she would sacrifice a sheep or the like, and would invite people, neighbours and friends, or distribute the meat among people. Praise be to Allah, her uncle got out safely, but Allah willed that the mother should die two years ago, without having fulfilled the vow. Is she now required to fulfil the vow on her mother’s behalf? Can she give money to the poor in Iraq? Please note that the daughter lives in Europe and it is difficult for her to fulfil the vow by slaughtering an animal.
Praise be to Allah.
    Firstly: 

    If a person makes a vow to sacrifice a sheep, for example, if 
    Allah saves his relative, this is a vow to do an act of worship which must 
    be fulfilled. If your mother died before fulfilling her vow, then it is 
    regarded as a debt that she owes and must be paid for out of her estate. If 
    she did not have any wealth, it is mustahabb for her children to do it on 
    her behalf. Al-Bukhaari (2761) and Muslim (1638) narrated from Ibn ‘Abbaas 
    (may Allah be pleased with him) that Sa‘d ibn ‘Ubaadah (may Allah be pleased 
    with him) asked the Messenger of Allah (blessings and peace of Allah be upon 
    him): My mother died, and had made a vow (that she did not fulfil). He said: 
    “Fulfil it on her behalf. 

    An-Nawawi (may Allah have mercy on him) said in Sharh 
    Muslim: The words of the Prophet (blessings and peace of Allah be upon 
    him), “Fulfil it on her behalf” indicate that obligations that were required 
    of the deceased should be fulfilled. With regard to financial obligations, 
    there is scholarly consensus (that the must be fulfilled). As for 
    obligations to do other acts of worship, there is a difference of scholarly 
    opinions concerning them. 

    Moreover, the view of ash-Shaafa‘i and others is that 
    financial obligations that were required of the deceased, such as zakaah, 
    expiation and vows, must be fulfilled, whether he left instructions to that 
    effect or not, as is the case with debts owed to people. 

    It should be noted that our view and that of the majority is 
    that the heir is not obliged to fulfil the vow that was obligatory upon the 
    deceased if it was not financial, or if it was financial but he did not 
    leave behind any estate, but it is mustahabb for him to do that. End quote. 

    Secondly: 

    If a person vows to sacrifice a sheep or the like, it is 
    obligatory for him to fulfil the vow, and it is not acceptable to pay the 
    cash value instead. The Standing Committee for Issuing Fatwas were asked 
    about a woman who vowed to sacrifice a lamb every month, but she found it 
    difficult to buy lambs, slaughter them and distribute the meat. Is it 
    permissible for her to give the cash value of the lambs? 

    They replied: 

    There is no hardship in sacrificing lambs; rather she has to 
    continue sacrificing them and distributing the meat to the poor, and it is 
    not acceptable for her to give the cash value, because the Prophet 
    (blessings and peace of Allah be upon him) said: “Whoever makes a vow to do 
    an act of obedience to Allah, let him do it, and whoever makes a vow to do 
    an act of disobedience to Allah, let him not do it.” End quote. 

    Shaykh ‘Abd al-‘Azeez ibn Baaz, Shaykh ‘Abdullah ibn 
    Ghadyaan, Shaykh ‘Abdullah ibn Qa‘ood. 

    Fataawa al-Lajnah ad-Daa’imah, 
    23/395 

    Based on that, it is not permissible to give the cash value 
    instead of slaughtering the sheep; the fact that the questioner lives in 
    Europe does not mean that she cannot delegate someone to sacrifice a sheep 
    and distribute the meat to neighbours and friends, either in the country 
    where she is living or elsewhere. 

    And Allah knows best.