It is Hated to Make Vows, But it is Obligatory to Fulfill Them

Question :

What is the ruling of the Islamic Law on swearing vows? And is there any punishment for not fulfilling a vow? And is it permissible to transfer the value of the thing which was dedicated to a share in some charitable work?

Answer:

The ruling of the Islamic Law on making vows is that it is hated, for it has been confirmed that the Prophet ﷺ said:
"No good comes of it; it is only a means by which something is removed from the miserly."

This is because some people, when they become ill, or lose something or are harmed in some way, vow to give charity or to slaughter an animal or give money if the illness, loss or harm is removed from them. They believe that Allah does not cure them or profit them unless they make this vow. The Prophet has informed us that Allah does not change anything He has predetermined or ordained, but he i.e. the one who makes the vow, is a miser, and would not spend (in charity) except after making a vow.

It is obligatory to fulfill a vow if it is an act of worship, such as a vow to offer a prayer, or to fast, or to give charity or to perform I'tikaf. But it is not permissible if the vow was to commit a sin, such as killing, illegal sexual intercourse, drinking wine, unjustly taking the wealth of another or the like. He must make atonement for an oath, which is to feed ten poor persons etc.

And if the vow was to do something which is merely allowed, such as eating, drinking, wearing clothes, normal speech or the like, he may choose between fulfilling the vow and making the atonement for an unfulfilled oath.

If he vowed in obedience to Allah to distribute something to the poor and the oppressed, such as food or the meat of a slaughtered sheep or the like, then he must distribute it to the poor and the oppressed. If it was a good deed - whether a physical act or a financial one, such as Jihad or Hajj and Umrah - then he must fulfill it; and if he declared it to be for a specific thing, such as the mosques, or books, or charitable works, he must keep it for them, and it is not permissible for him to disburse it for something other than that which he specified.

Source:
Ibn Jibreen
Fatawa Islamiyah, Vol. 6 Pages 410-411