Translation
(11) The Chapters on Expiation
كتاب الكفارات
(19) Chapter: One who dies with a vow left to fulfill
(19) باب مَنْ مَاتَ وَعَلَيْهِ نَذْرٌ
Sunan Ibn Majah 2133 
It was narrated from Jabir bin 'Abdullsh that :
a woman came to the Messenger of Allah (ﷺ) and said: "My mother has died, and she had made a vow to fast, but she died before she could fulfill it. The Messenger of Allah (ﷺ) said: 'Let her guardian fast on her behalf ."
حَدَّثَنَا مُحَمَّدُ بْنُ يَحْيَى، حَدَّثَنَا يَحْيَى بْنُ بُكَيْرٍ، حَدَّثَنَا ابْنُ لَهِيعَةَ، عَنْ عَمْرِو بْنِ دِينَارٍ، عَنْ جَابِرِ بْنِ عَبْدِ اللَّهِ، ‏.‏ أَنَّ امْرَأَةً، أَتَتْ رَسُولَ اللَّهِ ـ صلى الله عليه وسلم ـ فَقَالَتْ إِنَّ أُمِّي تُوُفِّيَتْ وَعَلَيْهَا نَذْرُ صِيَامٍ فَتُوُفِّيَتْ قَبْلَ أَنْ تَقْضِيَهُ ‏.‏ فَقَالَ رَسُولُ اللَّهِ ـ صلى الله عليه وسلم ـ ‏ "‏ لِيَصُمْ عَنْهَا الْوَلِيُّ ‏"‏ ‏.‏
Grade :  Da'if (Darussalam)
Reference : Sunan Ibn Majah 2133
In-book reference : Book 11, Hadith 44
English translation : Vol. 3, Book 11, Hadith 2133