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 ﷺ فَقَالَتْ إِنَّ أُمِّي تُوُفِّيَتْ وَعَلَيْهَا نَذْرُ صِيَامٍ فَتُوُفِّيَتْ قَبْلَ أَنْ تَقْضِيَهُ . فَقَالَ رَسُولُ اللَّهِ ﷺ " لِيَصُمْ عَنْهَا الْوَلِيُّ " .