There is nothing wrong with a woman giving charity from her husband’s wealth if he has given her permission to do so. This permission may be explicit (verbal), such as if he says to her: “You can give such and such of my wealth in charity, or whatever you wish.”
Or this permission may be implicit, such as if people ordinarily agree to such things or it is known from her husband’s attitude that he will agree to that and will not object.
In that case there is nothing wrong with her giving charity from her husband’s wealth, and she will have the reward for that charity as will her husband too.
But if he does not allow her, or if she knows that he would not agree to that, then in that case it is not permissible for her to give anything from his wealth in charity.
Ibn Qudaamah (may Allaah have mercy on him) said in al-Mughni (4/301):
Is it permissible for a woman to give a small amount in charity from her husband’s wealth without his permission? There are two views. One is that it is permissible, because ‘Aa’ishah said: The Messenger of Allaah (peace and blessings of Allaah be upon him) said: “No woman spends anything from her husband’s household, without causing any harm, but she will have the reward for that, and he will have a similar reward because he earned it, and she will have a reward because she spent it, and the storekeeper will have a similar reward, without it detracting from the reward of any of them in the slightest.” And he did not mention the issue of permission.
It was narrated from Asma’ that she came to the Prophet (peace and blessings of Allaah be upon him) and said: O Messenger of Allaah, I have nothing but that which al-Zubayr gives me. Is there any sin on me if I give charity from that which is given to me? He said: Give whatever you can. According to a report narrated by al-Bukhaari: “Give charity.” Agreed upon.
The custom is to allow that and agree to it, and this implies permission.
The second view is that it is not permitted, but the first view is more sound.
If he forbids her to do that and says “Do not give anything in charity, do not donate a small or large amount of my wealth,” then it is not permissible for her to do that. End quote.
The fact that it is not permissible for a woman to give any of her husband’s wealth in charity except with his permission is the hadeeth narrated by Abu Dawood (3565) from Abu Umaamah (may Allaah be pleased with him) who said: I heard the Messenger of Allaah (peace and blessings of Allaah be upon him) say: “A woman should not spend anything from her husband’s household except with his permission.” It was said: “O Messenger of Allaah, not even food?” He said: “That is the best of our wealth.” Classed as saheeh by al-Albaani in Saheeh Abi Dawood.
“Except with the permission of her husband” means explicit or implicit permission, as stated in ‘Awn al-Ma’bood.
The Standing Committee was asked about a woman who gave charity from her husband’s wealth without permission.
They replied: The basic principle is that a woman does not have the right to give any of her husband’s wealth in charity without his permission, except small things that are customarily given, such as upholding ties with neighbours and those who ask for help by giving small amounts that will not affect her husband, and the reward will be shared between them as the Prophet (peace and blessings of Allaah be upon him) said, … then they quoted the hadeeth of ‘Aa’ishah that is mentioned above. End quote.
Fataawa al-Lajnah al-Daa’imah (10/81).
Shaykh Ibn ‘Uthaymeen (may Allaah have mercy on him) was asked: Is it permissible for a woman to give charity from her husband’s wealth on her own behalf or on behalf of one who is dead?
He replied: It is well known that the husband’s wealth belongs to the husband and it is not permissible for anyone to give charity from the wealth of anyone else except with his permission. If the husband has given her permission to give charity on her own behalf, or on behalf of whomever she wishes among her deceased loved ones, there is no sin on her, but if he has not given permission then it is not permissible for her to give anything in charity, because it is his wealth and it is not permissible to take the wealth of a Muslim without his consent. End quote.
Majmoo’ Fataawa Ibn ‘Uthaymeen (18/472)
And Allaah knows best.