A woman vowed to perform Hajj but then died. Her brother came to the Prophet ﷺ and asked him about it.The Prophet ﷺ said, "Tell me, if your sister had a debt, would you pay it off?"He replied, "Yes."The Prophet ﷺ said, "Then fulfill what is owed to Allah, for He is more deserving of being repaid."
أخبرنا محمد بن بشار قال حدثنا محمد قال حدثنا شعبة عن أبي بشر قال سمعت سعيد بن جبير يحدث
أن امرأة نذرت أن تحج فماتت فأتى أخوها النبي ﷺ فسأله عن ذلك فقال أرأيت لو كان على أختك دين أكنت قاضيه قال نعم قال فاقضوا الله فهو أحق بالوفاء
Sourcing, sahih. Bukhari narrated it in the Book of Oaths and Vows, chapter of one who dies while a vow is still upon him, hadith no. 6699, from the hadith of Shubah, transmitted with this chain, and it is in Al-Kubra, hadith no. 3612.