It was narrated that Ibn 'Abbas said:

"Sa'd bin 'Ubadah Al-Ansari consulted the Messenger of Allah about an (outstanding) vow that his mother had to fulfill, but she died before doing so. The Messenger of Allah said: 'Fulfill it on her behalf.'"

أَخْبَرَنَا قُتَيْبَةُ بْنُ سَعِيدٍ، قَالَ حَدَّثَنَا اللَّيْثُ، عَنِ الزُّهْرِيِّ، عَنْ عُبَيْدِ اللَّهِ بْنِ عَبْدِ اللَّهِ، عَنِ ابْنِ عَبَّاسٍ، قَالَ اسْتَفْتَى سَعْدُ بْنُ عُبَادَةَ الأَنْصَارِيُّ رَسُولَ اللَّهِ ﷺ فِي نَذْرٍ كَانَ عَلَى أُمِّهِ فَتُوُفِّيَتْ قَبْلَ أَنْ تَقْضِيَهُ فَقَالَ رَسُولُ اللَّهِ ﷺ " اقْضِهِ عَنْهَا ".