He vowed to give 100,000 riyals in charity. Should he fulfil his vow?
Question

                A person said to Allaah, “If I do such and such, then I will give 100,000 riyals in charity.” Then he did that thing, but now he regrets it and does not want to give this large amount in charity. Is it permissible for him to offer kafaarat yameen (expiation for breaking a vow), or does he have to give this amount in charity, knowing that he has 400,000 riyals?.
Praise be to Allah.Yes, you have to fulfil your vow, because the Prophet  (peace and blessings of 
    Allaah be upon him) said: “Whoever vows to do an act of obedience to Allaah, then let him obey Him.” Narrated by al-Bukhaari, 6318. But there are 
    some matters to which attention must be paid: 
Firstly: 
The definition of a vow (nadhr) is when a person who is accountable (mukallaf) 
    commits himself to doing something that he is not obliged to do according to sharee’ah. 
Secondly: 
The Prophet  (peace and blessings of Allaah be upon him) forbade making vows. 
It was narrated that Ibn ‘Umar (may Allaah be pleased with him) said: The Prophet 
     (peace and blessings of Allaah be upon him) told us not to make vows and said, “They do not ward off anything that Allaah has decreed, rather 
    they are a means of getting charity from those who are stingy.”  
Al-Nawawi said: 
What is meant by the words “they are a means of getting charity from those who are stingy” is 
    that the stingy person does not do anything by his own initiative, rather he does it in return for healing of sickness or other reasons. 
Some of the scholars – including Shaykh al-Islam Ibn Taymiyah – are of the view 
    that vows are haraam, but the majority of scholars said that they are makrooh. However there is no difference of opinion concerning the fact that 
    if a person makes a vow, fulfilling his vow becomes obligatory. 
It was narrated from ‘Aa’ishah (may Allaah be pleased with her) that the Prophet 
     (peace and blessings of Allaah be upon him) said: “Whoever vows to do an act of obedience to Allaah, then let him obey Him, but whoever vows 
    to do an act of disobedience to Allaah, let him not disobey Him.” 
Narrated by al-Bukhaari, 6318 
Islam condemns those who make vows and do not fulfil them, and states that they 
    would come after the best generations. 
It was narrated that ‘Imraan ibn Husayn (may Allaah be pleased with him) said: The 
    Messenger of Allaah  (peace and blessings of Allaah be upon him) said: “The best of my ummah is my generation, then those who come after them, 
    then those who come after them.” ‘Imraan said, I do not know if he mentioned two or three generations after his. “Then after you there will come 
    people who will bear witness without being asked to do so, and will be treacherous and untrustworthy, and they will vow and never fulfill their 
    vows, and fatness will appear among them.” 
Narrated by al-Bukhaari, 2508; Muslim, 2535 
Based on this, the one who made this vow has to give the amount he vowed to give 
    in charity. It is not permissible for him not to fulfil his vow, and it is not sufficient for him to offer kafaarat yameen when he is able to pay 
    the amount he vowed to give in charity. 
It was narrated that Thaabit ibn al-Dahhaak said: At the time of the Messenger of Allaah  
    (peace and blessings of Allaah be upon him) a man vowed to sacrifice a camel in Buwaanah. He came to the Prophet  (peace and blessings of 
    Allaah be upon him) and said, “I vowed to sacrifice a camel in Buwaanah.” The Prophet  (peace and blessings of Allaah be upon him) said, “Is 
    there any idol of the Jaahiliyyah there that is worshipped?” He said, “No.” He said, “Are any of their festivals celebrated there?” He said, “No.” 
    The Messenger of Allaah  (peace and blessings of Allaah be upon him) said: “Fulfil your vow, for no vow should be fulfilled if it involves 
    disobedience towards Allaah or that which the son of Adam has no control over.” 
Narrated by Abu Dawood, 3313; classed as saheeh by al-Haafiz ibn Hajar in 
    al-Talkhees al-Habeer, 4/180. 
Al-San’aani said: 
This proves that the one who vows to give charity or to offer a sacrifice in a specific place 
    has the individual duty to fulfil his vow so long as there is nothing connected to the people of Jaahiliyyah in that place. 
Subul al-Salaam, 4/114  
But if his 
    intention in making this vow is to stop himself doing this action, then in 
    this case it comes under the ruling on kafaarat yameen (expiation for 
    breaking a vow) and he does not have to fulfil this vow. Please see question 
    no. 45889.
And Allaah knows best.