Language:
كتاب الأيمان والنذور
83  
Oaths and Vows
(30)
Chapter: If somebody dies without fulfiling a vow
(30)
باب مَنْ مَاتَ وَعَلَيْهِ نَذْرٌ
Sahih al-Bukhari 6699

Narrated Ibn `Abbas:

A man came to the Prophet (ﷺ) and said to him, "My sister vowed to perform the Hajj, but she died (before fulfilling it)." The Prophet (ﷺ) said, "Would you not have paid her debts if she had any?" The man said, "Yes." The Prophet (ﷺ) said, "So pay Allah's Rights, as He is more entitled to receive His rights."

حَدَّثَنَا آدَمُ، حَدَّثَنَا شُعْبَةُ، عَنْ أَبِي بِشْرٍ، قَالَ سَمِعْتُ سَعِيدَ بْنَ جُبَيْرٍ، عَنِ ابْنِ عَبَّاسٍ ـ رضى الله عنهما ـ قَالَ أَتَى رَجُلٌ النَّبِيَّ صلى الله عليه وسلم فَقَالَ لَهُ إِنَّ أُخْتِي نَذَرَتْ أَنْ تَحُجَّ وَإِنَّهَا مَاتَتْ‏.‏ فَقَالَ النَّبِيُّ صلى الله عليه وسلم ‏"‏ لَوْ كَانَ عَلَيْهَا دَيْنٌ أَكُنْتَ قَاضِيَهُ ‏"‏‏.‏ قَالَ نَعَمْ‏.‏ قَالَ ‏"‏ فَاقْضِ اللَّهَ، فَهْوَ أَحَقُّ بِالْقَضَاءِ ‏"‏‏.‏
Reference : Sahih al-Bukhari 6699
In-book reference : Book 83, Hadith 76
USC-MSA web (English) reference : Vol. 8, Book 78, Hadith 690
  (deprecated numbering scheme)