Paying off a father’s debt from zakaah
Question

                Is it permissible to pay off a father’s debt from zakaah?.
Praise be to Allah.
    If the father took on this debt in order to spend on himself, 
    it is not permissible for his son to give his zakaah to his father to pay 
    off his debt, because the son is obliged to spend on his father. 
But if this debt was for 
    something else other than spending on himself, then there is nothing wrong 
    with the son paying it off with zakaah, because he is not obliged to pay off 
    his father’s debt, so he is not avoiding an obligatory duty by doing so. 

    Shaykh Ibn Baaz said: 

    Paying zakaah to relatives who are entitled to it is better 
    than giving it to those who are not your relatives, because charity given to 
    relatives is both charity and upholding the ties of kinship, unless these 
    relatives are those on whom you are obliged to spend, in which case giving 
    zakaah to them in order to free yourself from the obligation to spend on 
    them is not permissible. If it so happens that these brothers and sisters 
    whom you have mentioned are poor, and you cannot afford to spend on them, 
    then there is nothing wrong with you giving them your zakaah. Similarly, if 
    these brothers and sisters owe debts to people and you pay off their debts 
    with your zakaah, there is nothing wrong with you doing that. That is 
    because a person is not obliged to pay off the debts of his relative, so if 
    he pays them off with his zakaah, that is something for which he will be 
    rewarded. Even if it is your son or father who owes a debt to someone and 
    cannot pay it off, it is permissible for you to pay off your father’s debt 
    from your zakaah, i.e., it is permissible for you to pay off your father’s 
    debt from your zakaah and it is permissible to pay off the debt of your son 
    from your zakaah, so long as the reason for this debt is not to obtain money 
    for maintenance that it is your duty to pay. If the reason for it is to 
    obtain maintenance which it is your duty to pay, then it is not permissible 
    for you to pay off the debt from your zakaah, lest you use that as a trick 
    to get out of spending on those on whom you are obliged to spend so that 
    they can take on debts and you can pay them off with your zakaah. End 
    quote. 

    Majmoo’ Fataawa Ibn Baaz, 
    14/310 

    Shaykh Ibn ‘Uthaymeen (may Allaah have mercy on him) said: 
If you are obliged to 
    spend on someone, it is not permissible for you to give zakaah to him as 
    maintenance, but if it is to pay off his debt, there is nothing wrong with 
    that. If we assume that a father owes a debt, and his son wants to pay off 
    his debt from his zakaah, and (the father) is unable to pay it off, there is 
    nothing wrong with that. The same applies to a mother or a son. But if you 
    are giving zakaah for the purpose of maintenance, that is not permissible, 
    because by doing this you are saving your money, but it is obligatory to 
    spend on one's parents, mother and father, and on sons and daughters, and on 
    everyone from whom you would inherit if he died, i.e., everyone from whom 
    you would inherit if he died, you are obliged to spend on, because Allaah 
    says (interpretation of the meaning):

    “And on the (father’s) heir is 
    incumbent the like of that (which was incumbent on the father)”

    [al-Baqarah 2:233]
Allaah has enjoined upon 
    the heir the payment for breastfeeding, because breastfeeding is like 
    spending. End quote.

    Fataawa Ibn ‘Uthaymeen, 
    18/416.