No need to fulfill a vow of which the reason ceased to exist before fulfilling the desired thing
12-8-2015 | IslamWeb
Question:
A woman made a vow that she would slaughter a sheep and distribute its meat among the poor if her husband was relieved of his distress. Now, he is relieved of his distress, but she is no longer his wife. The divorce took place shortly before the distress was relieved. Should she fulfill this vow?
Answer:
All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad 
is His slave and Messenger.
First, this kind of vow is forbidden because it does not bring about any benefit, neither does it ward off any harm nor fend off what is predestined. Ibn ‘Umar 
narrated that the Messenger of Allaah, sallallaahu ‘alayhi wa sallam, forbade them from making vows and said: "It does not (necessarily) bring good; it is a just a means by which something of the wealth of the stingy is spent." [Al-Bukhari and Muslim] However, it is incumbent on the person to fulfill such a vow when what he wished for happens. The Prophet, sallallaahu ‘alayhi wa sallam, said: "Whoever vowed to obey Allaah, must obey Him..." [Al-Bukhari and Muslim]
As for your question, if the reason that caused the vow to be made was your compassion towards your husband as he is your children's father or cousin or the like of the bonds that continue to exist even after divorce, then you are obliged to fulfill the vow. This is because the reason that caused the vow to be made still exists and the desired thing happened as the husband has actually been relieved of his distress. However, if the reason that caused the vow to be made was the wife's love, affection, and mercy for her husband that Allaah, the Exalted, has implanted in the hearts of the spouses, it is not incumbent on her to fulfill this vow because its reason ceased to exist as they were divorced before the desired thing happened. The same applies to a man who swears an oath that his wife should not go out of the house and then she goes out after being divorced from him irrevocably due to another reason (than that for which the oath was made). In this case, his oath is not considered broken.
Allaah Knows best.