Sunan an-Nasa'i, Volume 4, Book 30, Hadith 3693 (DarusSalam) ⓘ
It was narrated that Ibn 'Abbas said: Sa'd bin 'Ubadah came to the Prophet and said: "My mother has died and she had a vow to fulfill but she did not do so." He said: "Fulfill it on her behalf."
أَخْبَرَنَا هَارُونُ بْنُ إِسْحَاقَ الْهَمْدَانِيُّ، عَنْ عَبْدَةَ، عَنْ هِشَامٍ، - هُوَ ابْنُ عُرْوَةَ - عَنْ بَكْرِ بْنِ وَائِلٍ، عَنِ الزُّهْرِيِّ، عَنْ عُبَيْدِ اللَّهِ بْنِ عَبْدِ اللَّهِ، عَنِ ابْنِ عَبَّاسٍ، قَالَ جَاءَ سَعْدُ بْنُ عُبَادَةَ إِلَى النَّبِيِّ صلى الله عليه وسلم فَقَالَ إِنَّ أُمِّي مَاتَتْ وَعَلَيْهَا نَذْرٌ وَلَمْ تَقْضِهِ قَالَ " اقْضِهِ عَنْهَا " .
also referenced under: Hadith 3663 (Reference) & Book 30, Hadith 53 (In-Book)