Ruling on one who gives all his wealth in charity

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.