Firstly: The Ruling of Voluntary Charity
Voluntary charity is mustahabb. Consensus has been quoted on this by: al-Nawawi, Ibn Hajar al-Haytami, and all-Buhuti.
Secondly: The Ruling on Going Back on Voluntary Charity
It is not permissible to go back on voluntary charity once it has been given to its recipient. Consensus has been quoted on this by: Ibn Hazm and Ibn Hajar al-`Asqalani.
Thirdly: Voluntary Charity of a Woman from Her Wealth
It is permissible for an upright woman to do as she wishes with her wealth, regardless whether she is a virgin or not, married or unmarried, and regardless of she is dealing with a third of her wealth or more. This is the position of the majority: Hanafis, Shafi`is, and Hanbalis.
Fourthly: Voluntary Charity of a Woman from Her Husband’s Wealth
It is not for the woman to give voluntary charity from her husband’s wealth without his permission,  Al-Baghawi said: “This is what is acted upon according to the vast majority of scholars, that the woman does not spend from her husband’s wealth without his permission. Likewise the servant. They are both sinful if they do so.” Sharh al-Sunnah (206, 205/6) unless it is little that is commonly accepted, like helping neighbours or giving something small to those who ask that does not harm her husband. The reward goes then to both of them. This is by agreement of the four schools of jurisprudence.  Al-Nawawi said: “It is permissible for the woman to give voluntary charity for the beggar and the like, according to what he explicitly gave her permission for. She may also give from what he didn’t give permission for but is sure of his being fine with it. If she is not sure and she spends from his wealth, it is haram.” Al-Majmu` (244/6) Ibn Qudamah said: “It is not valid to use the woman as an analogy for other than her, since she may use her husband’s wealth out of common culture and give from it in voluntary charity since she is present at home while he is not. Cultural permission suffices in place of legal permission, such that it is as if he said to her: do this. If he prohibited her from doing so, telling her not to give in voluntary charity from his wealth, even a little, then she may not spend from it since the prohibition is clear and nullifies the cultural permission.” Al-Mughni (350, 349/4)
Fifthly: Charity on Behalf of the Deceased
It is permissible to give charity on behalf of the deceased, and its reward reaches them. Consensus ahs been quoted on this  Some scholars viewed that the reward only reaches one’s deceased parents, no one else. by: Ibn `Ab al-Bar, al-Nawawi, Ibn Taymiyyah, and Ibn al-Qayyim.
Sixthly: Voluntary Charity to the Family of the Prophet ﷺ
It is permissible to give voluntary charity to the family of the Prophet ﷺ. This is by agreement of the four schools of jurisprudence:  Ibn Qudamah said regarding the permissibility of giving voluntary charity to the family of the Prophet ﷺ: “there is no difference of opinion over kindness to the Hashemite, pardoning him, and delaying him [in returning debts, in not immediately showing retribution, showing forbearance to him, etc]” Al-Mughni (491/2). Ibn `Uthaymin said: “As for the voluntary charity, it may be paid to the Children of Hashim, and this is the position of the majority of scholars and the most correct opinion.” Sharh al-Mumti` (254/6). Hanafis, the relied upon position of the Malikis, the correct position of the Malikis, and the Hanbalis.
Seventhly: Voluntary Charity to the Disbeliever
It is permissible to give voluntary charity to the disbeliever as long as he is not warring. This is the position of the Hanafis, Malikis, the choice of al-Adhra`i and al-Shirbini from the Shafi`is, and chosen also by Ibn Baz and Ibn `Uthaymin.