وَعَنْ اِبْنِ عَبَّاسٍ رَضِيَ اَللَّهُ عَنْهُمَا
قَالَ: «اِسْتَفْتَى سَعْدُ بْنُ عُبَادَةَ رضى الله عنه رَسُولَ اَللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ فِي نَذْرٍ كَانَ عَلَى أُمِّهِ، تُوُفِّيَتْ قَبْلِ أَنْ تَقْضِيَهُ ? فَقَالَ: «اِقْضِهِ عَنْهَا»
Sad ibn Ubada asked the Messenger of Allah (sallallahu alayhi wa sallam) for a ruling regarding a vow taken by his mother who had died before fulfilling it, and he said, “Fulfill it on her behalf.”.
Bulugh al-Maram 1573, Book 13, Oaths and Vows, Hadith 18. 1 min read