Narrated Ibn Abbas (RA):

Sa'd bin Ubada asked Allah's Messenger (ﷺ) for a ruling regarding a vow taken by his mother who had died before fulfilling it, and he said, "Fulfill it on her behalf." [Agreed upon].

وَعَنْ اِبْنِ عَبَّاسٍ رَضِيَ اَللَّهُ عَنْهُمَا قَالَ: { اِسْتَفْتَى سَعْدُ بْنُ عُبَادَةَ ‏- رضى الله عنه ‏- رَسُولَ اَللَّهِ ‏- صلى الله عليه وسلم ‏-فِي نَذْرٍ كَانَ عَلَى أُمِّهِ, تُوُفِّيَتْ قَبْلِ أَنْ تَقْضِيَهُ ? فَقَالَ:

اِقْضِهِ عَنْهَا

} مُتَّفَقٌ عَلَيْهِ [1]‏ .‏