I made a vow that I would slaughter

Q: I am a widow, and when my husband died he left me with two children. I have a paternal uncle who has no children and also my children’s paternal aunt has no children, as her children died while they were still young. I suffered a lot from poverty when my children were young, so I made a vow that if my older son learned to drive and became independent, I would pay for my uncle and my children’s aunt to perform Hajj. My uncle was a Bedouin who had some livestock, and whenever I asked him to go for Hajj, he would say, "I will perform Hajj next year, In sha’a-Allah (if Allah wills)." He then became ill and died on 29/2/1411 A.H. So I was unable fulfill my vow as regards my uncle. I did send my children’s aunt to perform Hajj, but my uncle (may Allah be merciful to him) died before performing it. Would Your Eminence please give me a Fatwa (legal opinion from a qualified Muslim scholar) on my vow in regard to my uncle, who died before I could send him to perform Hajj. What should I do with regard to this vow?May Allah guide Your Eminence to what is good! May Allah bless you with the best! As-salamu ‘alaykum warahmatullah wabarakatuh (May Allah's Peace, Mercy, and Blessings be upon you!)

A: The vow you made to send your uncle to perform Hajj at your expense was a vow of obedience. It was authentically reported that the Prophet (peace be upon him) said, “Anyone who vows to obey Allah, should obey Him.” As your uncle refrained from performing Hajj whenever you offered it to him and he (may Allah be merciful to him) then died, there is no obligation on you. However, if you perform Hajj on his behalf or deputize someone to perform Hajj on his behalf, (Part No. 23; Page No. 313) this would be an act of charity towards him, which will be greatly rewarded.May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.