That Sa'd bin 'Ubadah asked the Messenger of Allah ﷺ about a vow that was due from his mother, who died before fulfilling it. The Prophet ﷺ said: "Fulfill it for her."  

أَنَّ سَعْدَ بْنَ عُبَادَةَ اسْتَفْتَى رَسُولَ اللَّهِ ﷺ فِي نَذْرٍ كَانَ عَلَى أُمِّهِ تُوُفِّيَتْ قَبْلَ أَنْ تَقْضِيَهُ فَقَالَ النَّبِيُّ ﷺ اقْضِهِ عَنْهَا