Ruling on one who gives all his wealth in charity
Question

                There is a man who owns a car and uses it as a taxi to meet the needs of his children. When some people asked him to donate to some people who were faced with calamity, this man donated this car and swore that he did not own anything else. Is this action of his Islamically acceptable?.
Praise be to Allah.
      Firstly: 

    There is no doubt that charity is one of the 
    best acts by means of which one may draw close to Allah. For more 
    information, see the answer to questions nos.
    22885 and
    36783. 

    Secondly: 

    If a person gives all his wealth in charity 
    and has nothing left, if there is someone on whom he is obliged to spend, 
    such as his children, wife and parents, and he does not have a job from 
    which he can earn money to spend on them, it is not permissible for him to 
    give all his wealth, because the Prophet (blessings and peace of Allah be 
    upon him) said: “It is sufficient sin for a man to neglect his dependents.” 
    Narrated by Abu Dawood; classed as saheeh by Shaykh al-Albaani (may Allah 
    have mercy on him).  

    And he (blessings and peace of Allah be upon 
    him) said: “If you leave your heirs independent of means, that is better 
    than leaving them to beg from people.” Narrated by al-Bukhaari, 2742. 

    Because giving charity is naafil and 
    spending on one’s children is obligatory, it is not permissible to give 
    precedence to a naafil act over one that is obligatory. 

    It says in Asna al-Mataalib (1/407): 
    If he gives in charity that which he needs for his dependents, that is not 
    permissible, because of the report, “It is sufficient sin for a man to 
    neglect his dependents” (narrated by Abu Dawood with a saheeh isnaad; a 
    similar report was narrated by Muslim), and because supporting them is 
    obligatory and takes precedence over that which is naafil. End quote. 

    It says in al-Furoo‘ (2/650): If a 
    person wants to give all his wealth in charity, if he has dependents and 
    they have enough to live on or he can earn enough for them, then it is 
    permissible, because of the story of [Abu Bakr] al-Siddeeq (may Allah be 
    pleased with him), otherwise it is not permissible. End quote. 

    He also said (2/650): Our companions said: 
    If he will harm himself or those on whom he is obliged to spend by doing 
    that, then it is a sin. End quote. 

    In Subul al-Salaam it says: al-Baaji, 
    who is one of the Maalikis, said: It is haraam to use up all of one’s wealth 
    in charity. End quote. 

    Shaykh Ibn ‘Uthaymeen (may Allah have mercy 
    on him) said: This makes it clear that what is required is to start with 
    that which is obligatory. The first obligation is to look after yourself; 
    start with yourself and then those whom you support. But there may be some 
    emergency situations in which giving precedence to people other than your 
    family is more important, such as dealing with the urgent case of a starving 
    person who is going to die. If you can save him by giving him food, and your 
    family will not die if you do not feed them right now, then in this case we 
    give precedence to the starving person so as to meet his urgent need. End 
    quote from Sharh al-Kaafi. 

    The reason why it is haraam is if those on 
    whom you are obliged to spend do not approve. But if they do approve, then 
    there is nothing wrong with giving all of one’s wealth in charity. 

    It says in Mataalib Ooli al-Nuha 
    (2/166): If a person gives something that will make him unable to meet the 
    needs of one on whom he is obliged to spend, such as his wife or relative, 
    then it is a sin, unless his dependents agree to give precedence to others 
    over themselves, and this is better, because Allah says (interpretation of 
    the meaning): “and give them (emigrants) preference over themselves even 
    though they were in need of that” [al-Hashr 59:9]. 

    And Allah knows best.