أَخْبَرَنِي هَارُونُ بْنُ عَبْدِ اللَّهِ، قَالَ حَدَّثَنَا عَفَّانُ، قَالَ حَدَّثَنَا سُلَيْمَانُ بْنُ كَثِيرٍ، عَنِ الزُّهْرِيِّ، عَنْ عُبَيْدِ اللَّهِ بْنِ عَبْدِ اللَّهِ، عَنِ ابْنِ عَبَّاسٍ، عَنْ سَعْدِ بْنِ عُبَادَةَ، أَنَّهُ أَتَى النَّبِيَّ صلى الله عليه وسلم فَقَالَ إِنَّ أُمِّي مَاتَتْ وَعَلَيْهَا نَذْرٌ أَفَيُجْزِئُ عَنْهَا أَنْ أَعْتِقَ عَنْهَا قَالَ ‏"‏ أَعْتِقْ عَنْ أُمِّكَ ‏"‏‏.‏

It was narrated from Sa'd bin 'Ubadah that he came to the Prophet and said: "My mother has died and she had a vow to fulfill. Will it suffice if I free a slave on her behalf?" He said: "Free a slave on behalf of your mother." Translation Not Available

Book Ref: Sunan An Nisai Book 30 Hadith 3656
Web Ref:  Sunan An Nisai Vol 4 Book 30 Hadith 3686