Died Before Fulfilling a Vow: Will He Be Forgiven?
13-6-2019 | IslamWeb
Question:
Asalamalikum, I hope you will be able to answer my question. If one dies having debt owed to Allah, such as vows, will Allah forgive them for that? What happens if the family doesnt know about the vows ? Will she punished in the grave?.
Answer:
All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad 
is His slave and Messenger.
Whoever died while he was disobedient to Allah by abandoning a Wajib (Islamic obligation) – whether it is failing to fulfill a vow after being able to fulfill it or any other obligations – then his matter is to Allah: He may forgive him if He so Wishes, and He may Punish him if He so Wishes in the grave or in the Hereafter or in both; so his matter is to Allah Who is the Most Merciful among the merciful.
His family are not sinful because such a person abandoned an obligation, whether they were aware of it or not as Allah Says (what means): {And every soul earns not [blame] except against itself, and no bearer of burdens will bear the burden of another.} [Quran 6:164]
Besides, the Prophet said in his Farewell pilgrimage: “No sinner commits a sin but it is against himself. No father is to be punished for the sins of his child, and no child is to be punished for the sins of his father.” [At-Tirmithi]
We have already clarified that the vow on the dead is of two kinds:
1- Money that he vowed to donate.
2- A pure act of worship that he vowed to do, like fasting or Hajj, and the like.
If the vow was money that the person had made a vow to donate during his life, and then he died before fulfilling it, then it should be given out from his inheritance before its division on the heirs, if he had left any money; because it is among the debts that come in priority over the will and the heirs.
If the vow was about fasting or Hajj and the like, then it is legislated for his guardian to fulfill it on his behalf. Al-Bukhari wrote a Chapter in his Saheeh: "Chapter of whoever dies while he had left a vow, and Ibn ‘Umar ordered a woman who vowed to pray a prayer in the mosque of Qubaa’ and he said: "Pray on her behalf." And Ibn ‘Abbaas said the same thing.
He then mentioned the Hadeeth of ‘Abdullah ibn ‘Abbaas 
: that Sa’d ibn ‘Ubaadah al-Ansaari asked the Prophet for a Fatwa about a vow that was due on his mother and she died before fulfilling it, so the Prophet issued a Fatwa to him to fulfill it on her behalf. This action became a Sunnah (a followed practice) from that time onwards. [Al-Bukhari]
For more benefit on someone who died before fulfilling a vow, please refer to Fataawa 58005 and 34472.
Allah knows best.